<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.2 20190208//EN" "http://jats.nlm.nih.gov/publishing/1.2/JATS-journalpublishing1.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="1.2" xml:lang="en">
    <front>
        <journal-meta>
            <journal-id journal-id-type="pmc">F1000Research</journal-id>
            <journal-title-group>
                <journal-title>F1000Research</journal-title>
            </journal-title-group>
            <issn pub-type="epub">2046-1402</issn>
            <publisher>
                <publisher-name>F1000 Research Limited</publisher-name>
                <publisher-loc>London, UK</publisher-loc>
            </publisher>
        </journal-meta>
        <article-meta>
            <article-id pub-id-type="doi">10.12688/f1000research.159711.1</article-id>
            <article-categories>
                <subj-group subj-group-type="heading">
                    <subject>Research Article</subject>
                </subj-group>
                <subj-group>
                    <subject>Articles</subject>
                </subj-group>
            </article-categories>
            <title-group>
                <article-title>On 
                    <italic>t</italic>-derivations of PMS-algebras</article-title>
                <fn-group content-type="pub-status">
                    <fn>
                        <p>[version 1; peer review: 2 approved]</p>
                    </fn>
                </fn-group>
            </title-group>
            <contrib-group>
                <contrib contrib-type="author" corresp="yes">
                    <name>
                        <surname>Melese Kassahun</surname>
                        <given-names>Nibret</given-names>
                    </name>
                    <role content-type="http://credit.niso.org/">Conceptualization</role>
                    <role content-type="http://credit.niso.org/">Data Curation</role>
                    <role content-type="http://credit.niso.org/">Formal Analysis</role>
                    <role content-type="http://credit.niso.org/">Funding Acquisition</role>
                    <role content-type="http://credit.niso.org/">Investigation</role>
                    <role content-type="http://credit.niso.org/">Methodology</role>
                    <role content-type="http://credit.niso.org/">Project Administration</role>
                    <role content-type="http://credit.niso.org/">Resources</role>
                    <role content-type="http://credit.niso.org/">Software</role>
                    <role content-type="http://credit.niso.org/">Visualization</role>
                    <role content-type="http://credit.niso.org/">Writing &#x2013; Original Draft Preparation</role>
                    <role content-type="http://credit.niso.org/">Writing &#x2013; Review &amp; Editing</role>
                    <uri content-type="orcid">https://orcid.org/0009-0004-5010-6943</uri>
                    <xref ref-type="corresp" rid="c1">a</xref>
                    <xref ref-type="aff" rid="a1">1</xref>
                    <xref ref-type="aff" rid="a2">2</xref>
                </contrib>
                <contrib contrib-type="author" corresp="no">
                    <name>
                        <surname>Assaye Alaba</surname>
                        <given-names>Berhanu</given-names>
                    </name>
                    <role content-type="http://credit.niso.org/">Conceptualization</role>
                    <role content-type="http://credit.niso.org/">Supervision</role>
                    <role content-type="http://credit.niso.org/">Validation</role>
                    <role content-type="http://credit.niso.org/">Writing &#x2013; Review &amp; Editing</role>
                    <xref ref-type="aff" rid="a1">1</xref>
                </contrib>
                <contrib contrib-type="author" corresp="no">
                    <name>
                        <surname>Gedamu Wondifraw</surname>
                        <given-names>Yohannes</given-names>
                    </name>
                    <role content-type="http://credit.niso.org/">Resources</role>
                    <role content-type="http://credit.niso.org/">Supervision</role>
                    <role content-type="http://credit.niso.org/">Validation</role>
                    <role content-type="http://credit.niso.org/">Visualization</role>
                    <xref ref-type="aff" rid="a1">1</xref>
                </contrib>
                <contrib contrib-type="author" corresp="no">
                    <name>
                        <surname>Teshome Wale</surname>
                        <given-names>Zelalem</given-names>
                    </name>
                    <role content-type="http://credit.niso.org/">Investigation</role>
                    <role content-type="http://credit.niso.org/">Methodology</role>
                    <role content-type="http://credit.niso.org/">Supervision</role>
                    <role content-type="http://credit.niso.org/">Validation</role>
                    <role content-type="http://credit.niso.org/">Visualization</role>
                    <role content-type="http://credit.niso.org/">Writing &#x2013; Review &amp; Editing</role>
                    <xref ref-type="aff" rid="a3">3</xref>
                </contrib>
                <aff id="a1">
                    <label>1</label>Mathematics, Bahir Dar University College of Science, Bahir Dar, Amhara, 6000, Ethiopia</aff>
                <aff id="a2">
                    <label>2</label>Mathematics, Debre Markos University College of Natural and Computational Science, Debre Markos, Amhara, None, Ethiopia</aff>
                <aff id="a3">
                    <label>3</label>Mathematics, Addis Ababa University College of Natural Sciences, Addis Ababa, Addis Ababa, 1000, Ethiopia</aff>
            </contrib-group>
            <author-notes>
                <corresp id="c1">
                    <label>a</label>
                    <email xlink:href="mailto:nibret.melese2010@gmail.com">nibret.melese2010@gmail.com</email>
                </corresp>
                <fn fn-type="conflict">
                    <p>No competing interests were disclosed.</p>
                </fn>
            </author-notes>
            <pub-date pub-type="epub">
                <day>13</day>
                <month>1</month>
                <year>2025</year>
            </pub-date>
            <pub-date pub-type="collection">
                <year>2025</year>
            </pub-date>
            <volume>14</volume>
            <elocation-id>70</elocation-id>
            <history>
                <date date-type="accepted">
                    <day>19</day>
                    <month>12</month>
                    <year>2024</year>
                </date>
            </history>
            <permissions>
                <copyright-statement>Copyright: &#x00a9; 2025 Melese Kassahun N et al.</copyright-statement>
                <copyright-year>2025</copyright-year>
                <license xlink:href="https://creativecommons.org/licenses/by/4.0/">
                    <license-p>This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</license-p>
                </license>
            </permissions>
            <self-uri content-type="pdf" xlink:href="https://f1000research.com/articles/14-70/pdf"/>
            <abstract>
                <sec>
                    <title>Background</title>
                    <p>PMS algebras are a type of algebraic structure that has been studied extensively in recent years. They are a generalization of several other algebraic structures, such as Boolean algebras and MV-algebras.</p>
                </sec>
                <sec>
                    <title>Methods</title>
                    <p>In this paper, we introduce the concept of t-derivations on PMS algebras. T-derivations are a type of mapping between PMS algebras that satisfies certain properties. We then study the properties of t-derivations and regular t-derivations on PMS algebras.</p>
                </sec>
                <sec>
                    <title>Results</title>
                    <p>We characterize further properties of t-derivations in the context of PMS algebras. We also investigate a novel result of t-derivations on the G-part of a PMS-algebra. Finally, we prove that the set of all t-derivations on a PMS-algebra forms a semigroup.</p>
                </sec>
                <sec>
                    <title>Conclusions</title>
                    <p>This paper provides a comprehensive study of t-derivations on PMS algebras. We have established several new results and characterized the properties of t-derivations in detail. Our results contribute to the further understanding of PMS algebras and their associated structures.</p>
                </sec>
            </abstract>
            <kwd-group kwd-group-type="author">
                <kwd>PMS-algebras</kwd>
                <kwd>derivations</kwd>
                <kwd>t-derivations</kwd>
                <kwd>semigroup</kwd>
            </kwd-group>
            <funding-group>
                <funding-statement>The author(s) declared that no grants were involved in supporting this work.</funding-statement>
            </funding-group>
        </article-meta>
    </front>
    <body>
        <sec id="sec5" sec-type="intro">
            <title>1. Introduction</title>
            <p>Iseki
                <sup>
                    <xref ref-type="bibr" rid="ref3">3</xref>
                </sup> introduced BCK-algebras, which are a type of abstract algebra, in his 1978 work. Additionally, Iseki
                <sup>
                    <xref ref-type="bibr" rid="ref4">4</xref>
                </sup> established another class of abstract algebras called BCI- algebras, which are an extension of BCK-algebras, in his research work. Furthermore, Iseki
                <sup>
                    <xref ref-type="bibr" rid="ref4">4</xref>
                </sup> studied and explored the algebraic properties of BCI-algebras. Also, Tamalibrasi and Megalai
                <sup>
                    <xref ref-type="bibr" rid="ref8">8</xref>
                </sup> introduced and studied TM-algebras based on propositional calculus. Moreover, Mostafa et al.
                <sup>
                    <xref ref-type="bibr" rid="ref9">9</xref>
                </sup> studied the concepts of KUS-algebras, KUS-ideals, and KUS-subalgebras, and their relationships were investigated. Sithar and Nagalakshmi
                <sup>
                    <xref ref-type="bibr" rid="ref11">11</xref>
                </sup> continued studying. PMS-algebras, which encompass the notions of BCK/BCI/TM/KUS algebras. They also discussed the ideals of PMS-algebras and studied their properties.</p>
            <p>Derivations are essential areas of study in algebraic structure theory, originating from invariant theory and Galois theory. Derivations were introduced in rings and near rings by many researchers. Based on derivations in rings and near-rings theory, Jun and Xin
                <sup>
                    <xref ref-type="bibr" rid="ref7">7</xref>
                </sup> expanded the notion of derivations to BCI-algebras. After derivations were intro- duced in various algebraic structures, derivations were extended to new concepts called t-derivations. As a result, t-derivations are studied and characterized in various algebraic structures. Muhiuddin and Al-Roqi
                <sup>
                    <xref ref-type="bibr" rid="ref10">10</xref>
                </sup> introduced the notion of t-derivations on BCI- algebras and characterized their interesting results based on the context of BCI-algebras in their 2012 work. In 2013, Ganeshkumar and Chandramouleeswaran
                <sup>
                    <xref ref-type="bibr" rid="ref2">2</xref>
                </sup> introduced the idea of t-derivations on TM-algebras, and they explored their basic properties. Jana et al.
                <sup>
                    <xref ref-type="bibr" rid="ref5">5</xref>
                </sup> established the notion of t-derivations on subtraction algebras with their essential properties in their 2017 work. Furthermore, in 2020, t-derivations were introduced on lattices and explored their properties based on lattice structures by Javed et al.
                <sup>
                    <xref ref-type="bibr" rid="ref6">6</xref>
                </sup> Re- cently, in 2021, Siswanti et al.
                <sup>
                    <xref ref-type="bibr" rid="ref12">12</xref>
                </sup> t-derivations were studied on BP-algebras, and their detailed properties were examined. Additionally, Ganesan and Kandaraj
                <sup>
                    <xref ref-type="bibr" rid="ref1">1</xref>
                </sup> t-derivations on BH-algebras were introduced in their 2021 research work. In this paper, we introduce t-derivations on PMS-algebras and investigate their nice properties based on the structure of PMS-algebras. We also define regular derivations on PMS-algebras and characterize their properties. Finally, we show that the set of all t-derivations on PMS-algebras is a semigroup.</p>
        </sec>
        <sec id="sec6">
            <title>2. Preliminaries</title>
            <p>In this section, we will address the concepts and basic properties of PMS-algebras that we need for the main results in the next sections. The following definitions and properties are taken from Sithar and Nagalakshmi.
                <sup>
                    <xref ref-type="bibr" rid="ref11">11</xref>
                </sup>
                <statement id="state1">
                    <label>Definition 2.1.</label>
                    <p>A PMS-algebra is an algebra (X; &#x22c6;, 0) of type (2, 0) with a constant &#x201c;0&#x201d; and a binary operation &#x201c;&#x22c6;&#x201d; satisfying the following axioms:
                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>0 &#x22c6; a = a;</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>(b &#x22c6; a) &#x22c6; (c &#x22c6; a) = c &#x22c6; b for all a, b, c &#x2208; X.</p>
                            </list-item>
                        </list>
                    </p>
                    <p>In X, we define a binary relation &#x201c;&#x2264;&#x201d; by: a &#x2264; b if and only if a &#x22c6; b = 0.</p>
                </statement>

                <statement id="state2">
                    <label>Proposition 2.2.</label>
                    <p>

                        <italic toggle="yes">In a</italic> PMS
                        <italic toggle="yes">-algebra</italic> (X; &#x22c6;, 0) 
                        <italic toggle="yes">the following properties hold for all</italic> a, b, c &#x2208; X.
                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>a &#x22c6; a = 0.</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>(b &#x22c6; a) &#x22c6; a = b.</p>
                            </list-item>
                            <list-item>
                                <label>(3)</label>
                                <p>a &#x22c6; (b &#x22c6; a) = b &#x22c6; 0.</p>
                            </list-item>
                            <list-item>
                                <label>(4)</label>
                                <p>(b &#x22c6; a) &#x22c6; c = (c &#x22c6; a) &#x22c6; b.</p>
                            </list-item>
                            <list-item>
                                <label>(5)</label>
                                <p>(a &#x22c6; b) &#x22c6; 0 = b &#x22c6; a = (0 &#x22c6; b) &#x22c6; (0 &#x22c6; a).</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state3">
                    <label>Definition 2.3.</label>
                    <p>Let S be a nonempty subset of a PMS-algebra (X; &#x22c6;, 0). Then S is called a PMS-subalgebra of X if a &#x2217; b &#x2208; S for all a, b &#x2208; S.</p>
                </statement>

                <statement id="state4">
                    <label>Definition 2.4.</label>
                    <p>Let X be a PMS-algebra. The set G (X) = {a &#x2208; X: a&#x22c6; 0 = a} is called the G-part of X.</p>
                </statement>

                <statement id="state5">
                    <label>Definition 2.5.</label>
                    <p>Let X be a PMS-algebra. The set B (X) = {a &#x2208; X: a&#x22c6; 0 = 0} is called the p-radical of X.</p>
                </statement>
            </p>
        </sec>
        <sec id="sec7">
            <title>3. t-derivations</title>
            <p>

                <statement id="state6">
                    <label>Remark 3.1.</label>
                    <p>Let (X; &#x22c6;, 0) be a PMS-algebra.
                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>If b &#x22c6; a = c &#x22c6; a, then b = c;</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>If a &#x22c6; b = a &#x22c6; c, then b = c for all a, b, c &#x2208; X.</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state7">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let a, b, c &#x2208; X.

                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>Assume that b &#x22c6; a = c &#x22c6; a</p>
                                <p>
Now b = 0 &#x22c6; b = (a &#x22c6; a) &#x22c6; b = (b &#x22c6; a) &#x22c6; a = (c &#x22c6; a) &#x22c6; a = (a &#x22c6; a) &#x22c6; c = 0 &#x22c6; c = c.</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>Suppose that a &#x22c6; b = a &#x22c6; c</p>
                                <p>
Now b &#x22c6; a = b &#x22c6; ((a &#x22c6; b) &#x22c6; b) = b &#x22c6; ((a &#x22c6; c) &#x22c6; b) = (a &#x22c6; c) &#x22c6; 0 = (0 &#x22c6; c) &#x22c6; a = c &#x22c6; a. Hence by (1), we get b = c. &#x25a0;
</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state8">
                    <label>Definition 3.2.</label>
                    <p>A PMS-algebra X is said to be associative if (x &#x22c6; y) &#x22c6; z = x &#x22c6; (y &#x22c6; z) for all x, y, z &#x2208; X.</p>
                </statement>

                <statement id="state9">
                    <label>Example 3.3.</label>
                    <p>Let X be the PMS-algebra with the following Cayley table.
                        <table-wrap id="T1" orientation="portrait" position="anchor">
                            <table content-type="article-table" frame="hsides">
                                <tbody>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">&#x22c6;</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">3</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">3</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">3</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">3</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">3</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">3</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                    </tr>
                                </tbody>
                            </table>
                        </table-wrap>
</p>
                    <p>Then (X; &#x22c6;, 0) is an associative PMS-algebra.</p>
                </statement>

                <statement id="state10">
                    <label>Definition 3.4.</label>
                    <p>Let X be a PMS-algebra. Then, for t &#x2208; X, define a self-map d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>: X&#x2192; X by d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = t &#x22c6; x for all x &#x2208; X.</p>
                </statement>

                <statement id="state11">
                    <label>Definition 3.5.</label>
                    <p>Let X be a PMS-algebra. Then, for t &#x2208; X, a self-map d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>: X&#x2192; X is said to be a (left, right)-t-derivation of X, denoted by, (l, r)-t-derivation if d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x &#x22c6; y) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; y) &#x2227; (x &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y)) for all x, y &#x2208; X.</p>
                </statement>

                <statement id="state12">
                    <label>Remark 3.6.</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> be a (l, r)-t-derivation on a PMS-algebra X. Then d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x &#x22c6; y) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; y for all x, y &#x2208; X.</p>
                </statement>

                <statement id="state13">
                    <label>Example 3.7.</label>
                    <p>Let X be an associative PMS-algebra with the following Cayley Table.
                        <table-wrap id="T2" orientation="portrait" position="anchor">
                            <table content-type="article-table" frame="hsides">
                                <tbody>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">&#x22c6;</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                    </tr>
                                </tbody>
                            </table>
                        </table-wrap>
</p>
                    <p>Define, when t = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = x, &#x2200;x &#x2208; X. when t = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 1. when t = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 0. Therefore, for each t &#x2208; X, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a (l, r)-t-derivation on X.</p>
                </statement>

                <statement id="state14">
                    <label>Definition 3.8.</label>
                    <p>Let X be a PMS-algebra. Then, for t &#x2208; X, a self-map d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>: X&#x2192; X is said to be a (l, r)-t-derivation of X, denoted by, (r, l)-t-derivation if d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x &#x22c6; y) = (x &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y)) &#x2227; (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; y) for all x, y &#x2208; X.</p>
                </statement>

                <statement id="state15">
                    <label>Remark 3.9.</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> be a (r, l)-t-derivation on a PMS-algebra X. Then d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x &#x22c6; y) = x &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y) for all x, y &#x2208; X.</p>
                </statement>

                <statement id="state16">
                    <label>Example 3.10.</label>
                    <p>Let X be a non-associative PMS-algebra with the following Cayley Table.
                        <table-wrap id="T3" orientation="portrait" position="anchor">
                            <table content-type="article-table" frame="hsides">
                                <tbody>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">&#x22c6;</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                    </tr>
                                    <tr>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">1</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">2</td>
                                        <td align="left" colspan="1" rowspan="1" valign="top">0</td>
                                    </tr>
                                </tbody>
                            </table>
                        </table-wrap>
</p>
                    <p>Define, when t = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = x, &#x2200;x &#x2208; X. when t = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 1.</p>
                    <p>when t = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 0.</p>
                    <p>Therefore, for each t &#x2208; X, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a (r, l)-t-derivation on X.</p>
                </statement>

                <statement id="state17">
                    <label>Proposition 3.11.</label>
                    <p>

                        <italic toggle="yes">Let</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a self-map on a PMS-algebra
</italic> X
                        <italic toggle="yes">. Then</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> is a</italic> (r, l)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic> X.</p>
                </statement>

                <statement id="state18">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>: X&#x2192; X defined by d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = t &#x22c6; x. Now for x, y &#x2208; X,

                        <disp-formula id="e1">

                            <mml:math display="block">
                                <mml:mtable columnalign="left" displaystyle="true">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">t</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="5.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">t</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="5.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">t</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="0.6em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">t</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                            </mml:mrow>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                            <mml:mo stretchy="true">)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>
</disp-formula>
                    </p>
                    <p>Hence d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a (r, l)-t-derivation on X. &#x25a0;</p>
                </statement>

                <statement id="state19">
                    <label>Definition 3.12.</label>
                    <p>Let X be a PMS-algebra. Then, for t &#x2208; X, a self-map d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>: X&#x2192; X is called the t-derivation on X if d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is both a (l, r)-t-derivation and a (r, l)-t-derivation on X.</p>
                </statement>

                <statement id="state20">
                    <label>Example 3.13.</label>
                    <p>Consider the PMS-algebra X in 
                        <xref ref-type="statement" rid="state9">Example 3.3</xref>. Define the mapping d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> as follows:</p>
                    <p>When t = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = x, &#x2200;x &#x2208; X.</p>
                    <p>When t = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 3, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(3) = 2.</p>
                    <p>When t = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 3, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 0, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(3) = 1.</p>
                    <p>When t = 3, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 3, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(1) = 2, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(2) = 1, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(3) = 0. Therefore, for each t &#x2208; X, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a t-derivation of X.</p>
                </statement>

                <statement id="state21">
                    <label>Proposition 3.14.</label>
                    <p>

                        <italic toggle="yes">Let</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a self-map on an associative</italic> PMS
                        <italic toggle="yes">-algebra</italic> X
                        <italic toggle="yes">. Then</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> is a</italic> (l, r)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic> X.</p>
                </statement>

                <statement id="state22">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let X be an associative PMS-algebra and d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> be a self-map on X.
                        <disp-formula id="e2">

                            <mml:math display="block">
                                <mml:mtable columnalign="left" displaystyle="true">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">t</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="5.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">t</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="5.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>
</disp-formula>
                    </p>
                    <p>Hence d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is (r, l)-t-derivation on X.</p>
                    <p>By combining 
                        <xref ref-type="statement" rid="state17">Proposition 3.11</xref> and 
                        <xref ref-type="statement" rid="state21">Proposition 3.14</xref>, we get the following theorem. &#x25a0;</p>
                </statement>

                <statement id="state23">
                    <label>Theorem 3.15.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be an associative</italic> PMS
                        <italic toggle="yes">-algebra. For t</italic> &#x2208; X
                        <italic toggle="yes">, a self-map
</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> is a</italic> t
                        <italic toggle="yes">-derivation on</italic> X.</p>
                </statement>

                <statement id="state24">
                    <label>Definition 3.16.</label>
                    <p>A self-map d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> on a PMS-algebra X is said to be t-regular if d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 0.</p>
                </statement>

                <statement id="state25">
                    <label>Example 3.17.</label>
                    <p>In 
                        <xref ref-type="statement" rid="state20">Example 3.13</xref>, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a regular t-derivation on X where t = 0. However, for t = 1, t = 2, or t = 3, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is not a regular t-derivation on X.</p>
                </statement>

                <statement id="state26">
                    <label>Proposition 3.18.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be the</italic> p
                        <italic toggle="yes">-radical of a</italic> PMS
                        <italic toggle="yes">-algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a self-map on</italic> X
                        <italic toggle="yes">. Then</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> is</italic> t
                        <italic toggle="yes">-regular.</italic>
                    </p>
                </statement>

                <statement id="state27">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let X be a p-radical PMS-algebra.</p>
                    <p>Let x &#x2208; X. Then x &#x22c6; 0 = 0. Now d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = t &#x22c6; 0 = 0. Hence d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is t-regular. &#x25a0;</p>
                </statement>

                <statement id="state28">
                    <label>Theorem 3.19.</label>
                    <p>

                        <italic toggle="yes">Let</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a self-map on a</italic> PMS
                        <italic toggle="yes">-algebra</italic> X
                        <italic toggle="yes">. Then</italic>

                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>

                                    <italic toggle="yes">If</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub> is a</italic> (l, r)
                                    <italic toggle="yes">-</italic>t
                                    <italic toggle="yes">-derivation on</italic> X
                                    <italic toggle="yes">, then</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = x &#x2227; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x2200;x &#x2208; X 
                                    <italic toggle="yes">if and only if</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub> is</italic> t
                                    <italic toggle="yes">-regular.</italic>
                                </p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>

                                    <italic toggle="yes">If</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub> is a</italic> (r, l)
                                    <italic toggle="yes">-</italic>t
                                    <italic toggle="yes">-derivation on</italic> X
                                    <italic toggle="yes">. If</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub> is</italic> t
                                    <italic toggle="yes">-regular on</italic> X
                                    <italic toggle="yes">, then</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x2227; x &#x2200;x &#x2208; X.
</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state29">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>(1) Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a (l, r)-t-derivation on X. Suppose that d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = x &#x2227; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x).</p>
                    <p>
d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 0 &#x2227; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = (0 &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0)) &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0)) &#x22c6; 0 = 0 &#x22c6; 0 = 0.</p>
                    <p>
d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is regualr on X.</p>
                    <p>
Conversely, assume that d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is regular.</p>
                    <p>
Now d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0 &#x22c6; x) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) &#x22c6; x) &#x2227; (0 &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x)) = (0 &#x22c6; x) &#x2227; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = x &#x2227; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x). Hence d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = x &#x2227; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x)</p>
                    <p>
(2) Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is a (r, l)-t-derivation on X.</p>
                    <p>
Suppose d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 0.</p>
                    <p>
Now d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0 &#x22c6; x) = (0 &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) &#x22c6; x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; (0 &#x22c6; x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; x &#x25a0;</p>
                </statement>

                <statement id="state30">
                    <label>Theorem 3.20.</label>
                    <p>

                        <italic toggle="yes">Let</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a</italic> (r, l)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on a</italic> PMS
                        <italic toggle="yes">-algebra. Then the following holds true.</italic>

                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0) = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x), &#x2200;x &#x2208; X.</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>d
                                    <italic toggle="yes">
                                        <sub>t</sub> is one-to-one.</italic>
                                </p>
                            </list-item>
                            <list-item>
                                <label>(3)</label>
                                <p>

                                    <italic toggle="yes">If</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub> is</italic> t
                                    <italic toggle="yes">-regular, then it is the identity map.</italic>
                                </p>
                            </list-item>
                            <list-item>
                                <label>(4)</label>
                                <p>

                                    <italic toggle="yes">If there is an element</italic> x &#x2208; X 
                                    <italic toggle="yes">such that</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = x
                                    <italic toggle="yes">, then</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub> is the identity map.</italic>
                                </p>
                            </list-item>
                            <list-item>
                                <label>(5)</label>
                                <p>

                                    <italic toggle="yes">If</italic> x &#x2264; y
                                    <italic toggle="yes">, then</italic> d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x2264; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y) 
                                    <italic toggle="yes">for all</italic> x, y &#x2208; X.
</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state31">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> be a (r, l)-t-derivation on a PMS-algebra.
                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>Let x &#x2208; X. Then d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0) = t &#x22c6; 0 = t &#x22c6; (x &#x22c6; x) = x &#x22c6; (t &#x22c6; x) = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x).</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>Let x, y &#x2208; X such that d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y). Then t &#x22c6; x = t &#x22c6; y. Now
                                    <disp-formula id="e3">

                                        <mml:math display="block">
                                            <mml:mtable columnalign="left" displaystyle="true">
                                                <mml:mtr>
                                                    <mml:mtd>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mi mathvariant="normal">t</mml:mi>
                                                        <mml:mo>=</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mo stretchy="true">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mo stretchy="true">(</mml:mo>
                                                                <mml:mi mathvariant="normal">t</mml:mi>
                                                                <mml:mo>&#x22c6;</mml:mo>
                                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                                <mml:mo stretchy="true">)</mml:mo>
                                                            </mml:mrow>
                                                            <mml:mo>&#x22c6;</mml:mo>
                                                            <mml:mi mathvariant="normal">x</mml:mi>
                                                            <mml:mo stretchy="true">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mtd>
                                                </mml:mtr>
                                                <mml:mtr>
                                                    <mml:mtd>
                                                        <mml:mspace width="2.8em"/>
                                                        <mml:mo>=</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mo stretchy="true">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mo stretchy="true">(</mml:mo>
                                                                <mml:mi mathvariant="normal">t</mml:mi>
                                                                <mml:mo>&#x22c6;</mml:mo>
                                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                                <mml:mo stretchy="true">)</mml:mo>
                                                            </mml:mrow>
                                                            <mml:mo>&#x22c6;</mml:mo>
                                                            <mml:mi mathvariant="normal">x</mml:mi>
                                                            <mml:mo stretchy="true">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mtd>
                                                </mml:mtr>
                                                <mml:mtr>
                                                    <mml:mtd>
                                                        <mml:mspace width="2.8em"/>
                                                        <mml:mo>=</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mo stretchy="true">(</mml:mo>
                                                            <mml:mn>0</mml:mn>
                                                            <mml:mo>&#x22c6;</mml:mo>
                                                            <mml:mi mathvariant="normal">x</mml:mi>
                                                            <mml:mo stretchy="true">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mo stretchy="true">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mo stretchy="true">(</mml:mo>
                                                                <mml:mi mathvariant="normal">t</mml:mi>
                                                                <mml:mo>&#x22c6;</mml:mo>
                                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                                <mml:mo stretchy="true">)</mml:mo>
                                                            </mml:mrow>
                                                            <mml:mo>&#x22c6;</mml:mo>
                                                            <mml:mi mathvariant="normal">x</mml:mi>
                                                            <mml:mo stretchy="true">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mtd>
                                                </mml:mtr>
                                                <mml:mtr>
                                                    <mml:mtd>
                                                        <mml:mspace width="2.8em"/>
                                                        <mml:mo>=</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mo stretchy="true">(</mml:mo>
                                                            <mml:mi mathvariant="normal">t</mml:mi>
                                                            <mml:mo>&#x22c6;</mml:mo>
                                                            <mml:mi mathvariant="normal">y</mml:mi>
                                                            <mml:mo stretchy="true">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mtd>
                                                </mml:mtr>
                                                <mml:mtr>
                                                    <mml:mtd>
                                                        <mml:mspace width="2.8em"/>
                                                        <mml:mo>=</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mo stretchy="true">(</mml:mo>
                                                            <mml:mn>0</mml:mn>
                                                            <mml:mo>&#x22c6;</mml:mo>
                                                            <mml:mi mathvariant="normal">y</mml:mi>
                                                            <mml:mo stretchy="true">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mi mathvariant="normal">t</mml:mi>
                                                    </mml:mtd>
                                                </mml:mtr>
                                                <mml:mtr>
                                                    <mml:mtd>
                                                        <mml:mspace width="2.8em"/>
                                                        <mml:mo>=</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo>&#x22c6;</mml:mo>
                                                        <mml:mi mathvariant="normal">t</mml:mi>
                                                        <mml:mo>.</mml:mo>
                                                    </mml:mtd>
                                                </mml:mtr>
                                            </mml:mtable>
                                        </mml:math>
</disp-formula>
                                </p>
                                <p>
Hence by right cancellation, x = y. Therefore d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic> is an identity map.</p>
                            </list-item>
                            <list-item>
                                <label>(3)</label>
                                <p>Let d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic> be a t-regualr derivation on X.</p>
                                <p>
By (1), we have 0 = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0) = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) implies that x &#x22c6; x = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) Hence by left cancellation, d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = x.</p>
                            </list-item>
                            <list-item>
                                <label>(4)</label>
                                <p>Let d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = x for some x &#x2208; X.</p>
                                <p>
Now 0 = x &#x22c6; x = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x &#x22c6; x) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0) implies that d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic> is regular. Hence by (3) d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic> is an identity map.</p>
                            </list-item>
                            <list-item>
                                <label>(5)</label>
                                <p>Let x &#x2264; y. Then x &#x22c6; y = 0.</p>
                                <p>
Now d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x)&#x22c6;d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y) = (t&#x22c6;x)&#x22c6;(t&#x22c6;y) = ((t&#x22c6;y)&#x22c6;x)&#x22c6;t = ((x&#x22c6;y)&#x22c6;t)&#x22c6;t = (t&#x22c6;t)&#x22c6;(x&#x22c6;y) = 0 &#x22c6; 0 = 0.</p>
                                <p>
Hence d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x2264; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y). &#x25a0;
</p>
                            </list-item>
                        </list>
</p>
                </statement>

                <statement id="state32">
                    <label>Theorem 3.21.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a</italic> t
                        <italic toggle="yes">-derivation on</italic> X
                        <italic toggle="yes">. If</italic> y &#x2264; x 
                        <italic toggle="yes">and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x &#x22c6; y) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y) 
                        <italic toggle="yes">for all</italic> x, y &#x2208; X
                        <italic toggle="yes">,t hen</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y).</p>
                </statement>

                <statement id="state33">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let x &#x2264; y and d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x &#x22c6; y) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y).</p>
                    <p>Now for x &#x2208; X, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0&#x22c6;x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>((y&#x22c6;x)&#x22c6;x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y&#x22c6;x)&#x22c6;d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y)&#x22c6;d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x))&#x22c6;d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x)) &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y) = 0 &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y).</p>
                    <p>Hence d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(y).&#x25a0;</p>
                </statement>

                <statement id="state34">
                    <label>Theorem 3.22.</label>
                    <p>

                        <italic toggle="yes">Let</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a</italic> t
                        <italic toggle="yes">-regular</italic> (l, r)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on a</italic> PMS
                        <italic toggle="yes">-algebra</italic> X
                        <italic toggle="yes">. Then the following hold.</italic>

                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = x.</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; y = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y) 
                                    <italic toggle="yes">for all</italic> x, y &#x2208; X.</p>
                            </list-item>
                            <list-item>
                                <label>(3)</label>
                                <p>d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x &#x22c6; y) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; y = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y) = x &#x22c6; y.</p>
                            </list-item>
                            <list-item>
                                <label>(4)</label>
                                <p>Ker(d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>) = {x &#x2208; X: d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = 0} 
                                    <italic toggle="yes">is a subalgebra of</italic> X
                                    <italic toggle="yes">.</italic>
</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state61">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> be a t-regular (l, r)-t-derivation on a PMS-algebra
 X.
                        <list list-type="order">
                            <list-item>
                                <label>(1)</label>
                                <p>Let x &#x2208; X. Then d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0 &#x22c6; x) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0) &#x22c6; x = 0 &#x22c6; x = x.</p>
                            </list-item>
                            <list-item>
                                <label>(2)</label>
                                <p>Let x, y &#x2208; X. Then d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; y = x &#x22c6; y = x &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y).</p>
                            </list-item>
                            <list-item>
                                <label>(3)</label>
                                <p>Let x, y &#x2208; X. Then d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x &#x22c6; y) = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; y = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y) = x &#x22c6; y.</p>
                            </list-item>
                            <list-item>
                                <label>(4)</label>
                                <p>Since d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic> is regular, d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(0) = 0. Hence 0 &#x2208; Ker(d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>) Thus ker(d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>) is nonempty.</p>
                                <p>
Let x, y &#x2208; Ker(d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>). Then d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) = 0, d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(Y) = 0. Now d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x &#x22c6; y) = x &#x22c6; y = d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(x) &#x22c6; d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>(y) = 0 &#x22c6; 0 = 0. Hence x &#x22c6; y &#x2208; Ker(d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>).</p>
                                <p>
Therefore Ker(d
                                    <italic toggle="yes">
                                        <sub>t</sub>
                                    </italic>) is a subalgebra of X. &#x25a0;
</p>
                            </list-item>
                        </list>
                    </p>
                </statement>

                <statement id="state35">
                    <label>Theorem 3.23.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra. Then</italic> Ker(d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>) = {0} 
                        <italic toggle="yes">if and only if</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> is</italic> t
                        <italic toggle="yes">-regular.</italic>
                    </p>
                </statement>

                <statement id="state36">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Suppose Ker(d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>) = {0}. Then d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) = 0 &#x2200;x &#x2208; X. In particular, d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(0) = 0. Hence d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is regular.</p>
                    <p>Conversely, assume d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> is regular. Let x &#x2208; Ker(d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>). Then d
                        <sub>t</sub>(x) = 0. Now
                        <disp-formula id="e16">

                            <mml:math display="block">
                                <mml:mn>0</mml:mn>
                                <mml:mo>=</mml:mo>
                                <mml:msub>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi mathvariant="normal">t</mml:mi>
                                </mml:msub>
                                <mml:mrow>
                                    <mml:mo stretchy="true">(</mml:mo>
                                    <mml:mn>0</mml:mn>
                                    <mml:mo stretchy="true">)</mml:mo>
                                </mml:mrow>
                                <mml:mo>=</mml:mo>
                                <mml:msub>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi mathvariant="normal">t</mml:mi>
                                </mml:msub>
                                <mml:mrow>
                                    <mml:mo stretchy="true">(</mml:mo>
                                    <mml:mi mathvariant="normal">x</mml:mi>
                                    <mml:mo>&#x22c6;</mml:mo>
                                    <mml:mi mathvariant="normal">x</mml:mi>
                                    <mml:mo stretchy="true">)</mml:mo>
                                </mml:mrow>
                                <mml:mo>=</mml:mo>
                                <mml:msub>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi mathvariant="normal">t</mml:mi>
                                </mml:msub>
                                <mml:mrow>
                                    <mml:mo stretchy="true">(</mml:mo>
                                    <mml:mi mathvariant="normal">x</mml:mi>
                                    <mml:mo stretchy="true">)</mml:mo>
                                </mml:mrow>
                                <mml:mo>&#x22c6;</mml:mo>
                                <mml:mi mathvariant="normal">x</mml:mi>
                                <mml:mo>=</mml:mo>
                                <mml:mn>0</mml:mn>
                                <mml:mo>&#x22c6;</mml:mo>
                                <mml:mi mathvariant="normal">x</mml:mi>
                                <mml:mo>=</mml:mo>
                                <mml:mi mathvariant="normal">x</mml:mi>
                                <mml:mo>.</mml:mo>
                            </mml:math>
</disp-formula>
                    </p>
                    <p>Thus x = 0 implies that Ker(d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>) = {0} &#x25a0;</p>
                </statement>

                <statement id="state37">
                    <label>Definition 3.24.</label>
                    <p>Let X be a PMS-algebra and d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> be self-maps on X. Then define a mapping d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>: X &#x2192; X by (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x)) for all x &#x2208; X.</p>
                </statement>

                <statement id="state38">
                    <label>Theorem 3.25.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <italic toggle="yes">be a</italic> (l, r)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic> X
                        <italic toggle="yes">. Then</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) 
                        <italic toggle="yes">is a</italic> (l, r)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic>
 X.</p>
                </statement>

                <statement id="state39">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let X be a PMS-algebra and d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> be a (l, r)-t-derivation on X.</p>
                    <p>For x, y &#x2208; X, we have
                        <disp-formula id="e4">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.3em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.3em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.3em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>
</disp-formula>
                    </p>
                    <p>Hence (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) is a (l, r)- t-derivation of X. &#x25a0;</p>
                </statement>

                <statement id="state40">
                    <label>Theorem 3.26.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a PMS algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> d
                        <sup>'</sup>
                        <italic toggle="yes">
                            <sub>t</sub> be a</italic> (r, l)
                        <italic toggle="yes">-</italic> t
                        <italic toggle="yes">-derivation of</italic> X
                        <italic toggle="yes">. Then</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) 
                        <italic toggle="yes">is a</italic> (r, l)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic>
 X.</p>
                </statement>

                <statement id="state41">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let X be a PMS-algebra and d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> be a (r, l)-t-derivation on X.</p>
                    <p>For x, y &#x2208; X, we have
                        <disp-formula id="e5">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>
</disp-formula>
                    </p>
                    <p>Hence (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) is a (r, l)-t-derivation of X.</p>
                    <p>Combining 
                        <xref ref-type="statement" rid="state38">

                            <bold>Theorem</bold> 3.25</xref> and 
                        <xref ref-type="statement" rid="state40">

                            <bold>Theorem</bold> 3.26</xref>, we get the following theorem. &#x25a0;</p>
                </statement>

                <statement id="state42">
                    <label>Theorem 3.27.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <italic toggle="yes">be</italic> t
                        <italic toggle="yes">-derivation of</italic> X
                        <italic toggle="yes">. Then</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) 
                        <italic toggle="yes">is a</italic> t
                        <italic toggle="yes">-derivation on</italic> X.</p>
                </statement>

                <statement id="state43">
                    <label>Theorem 3.28.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra. Let</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> be a</italic> (r, l)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic> X 
                        <italic toggle="yes">and</italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <italic toggle="yes">be a</italic> (l, r)-t-

                        <italic toggle="yes">derivation on</italic> X. 
                        <italic toggle="yes">Then</italic> d
                        <sub>t</sub> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> = 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x25e6; d
                        <sub>t</sub>.</p>
                </statement>

                <statement id="state44">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> be a (r, l)-t-derivation on X and 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> be a (l, r)-t-derivation on X. Now
                        <disp-formula id="e6">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="7.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="7.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="7.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.1)</label>
</disp-formula>

                        <disp-formula id="e7">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x25e6;</mml:mo>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="7.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="7.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="7.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.2)</label>
</disp-formula>
                    </p>
                    <p>From 
                        <xref ref-type="disp-formula" rid="e6">(3.1)</xref> and 
                        <xref ref-type="disp-formula" rid="e7">(3.2)</xref> we have, (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = (
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x25e6; d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>)(x), &#x2200;x &#x2208; X. Thus d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> = 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x25e6; d
                        <sub>t</sub>. &#x25a0;</p>
                </statement>

                <statement id="state45">
                    <label>Theorem 3.29.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <italic toggle="yes">be two</italic> t
                        <italic toggle="yes">-derivations on</italic> X
                        <italic toggle="yes">, then</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x25e6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> = 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x25e6; d
                        <italic toggle="yes">
                            <sub>t</sub>.</italic>
                    </p>
                </statement>

                <statement id="state46">
                    <label>Definition 3.30.</label>
                    <p>Let X be a PMS-algebra and d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> be self-maps on X. Then define d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x22c6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>: X&#x2192; X by (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x22c6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x22c6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x) for all x &#x2208; X.</p>
                </statement>

                <statement id="state47">
                    <label>Theorem 3.31.</label>
                    <p>

                        <italic toggle="yes">Let</italic> X 
                        <italic toggle="yes">be a</italic> PMS
                        <italic toggle="yes">-algebra and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <italic toggle="yes">be</italic> t
                        <italic toggle="yes">-derivations on</italic> X
                        <italic toggle="yes">. Then</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x22c6; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> = 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x22c6; d
                        <italic toggle="yes">
                            <sub>t</sub>.</italic>
                    </p>
                </statement>

                <statement id="state48">
                    <label>Definition 3.32.</label>
                    <p>Let LDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X) be the set of all (l, r)-t-derivations on a PMS-algebra X. Then define a binary operation &#x201c;&#x2227;&#x201d; on LDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X) by (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> (x) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x), &#x2200;x &#x2208; X, where d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; LDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X).</p>
                </statement>

                <statement id="state49">
                    <label>Lemma 3.33.</label>
                    <p>

                        <italic toggle="yes">If</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> and</italic> d
                        <sup>'</sup>
                        <italic toggle="yes">
                            <sub>t</sub> are</italic> (l, r)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivations on</italic> X
                        <italic toggle="yes">. Then</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) 
                        <italic toggle="yes">is a</italic> (l, r)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic> X.</p>
                </statement>

                <statement id="state50">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>

                        <disp-formula id="e8">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">Y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.3)</label>
</disp-formula>

                        <disp-formula id="e9">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">y</mml:mi>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.4)</label>
</disp-formula>
                    </p>
                    <p>From 
                        <xref ref-type="disp-formula" rid="e8">(3.3)</xref> and 
                        <xref ref-type="disp-formula" rid="e9">(3.4)</xref>, we get (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x &#x22c6; y) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) &#x22c6; y. &#x25a0;</p>
                </statement>

                <statement id="state51">
                    <label>Lemma 3.34.</label>
                    <p>

                        <italic toggle="yes">The binary operation</italic> &#x2227; 
                        <italic toggle="yes">defined on</italic> L
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X) 
                        <italic toggle="yes">is associative.</italic>
                    </p>
                </statement>

                <statement id="state52">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2033;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; LDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X). Now for x &#x2208; X,

                        <disp-formula id="e10">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mo>&#x2227;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi>d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2032;</mml:mo>
                                                <mml:mo>&#x2032;</mml:mo>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="13.8em"/>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="13.8em"/>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.5)</label>
</disp-formula>

                        <disp-formula id="e11">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mo>&#x2227;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2033;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                    <mml:msub>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                                <mml:msub>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:msub>
                                                        <mml:mo>&#x2033;</mml:mo>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:msub>
                                                        <mml:mo>&#x2033;</mml:mo>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="12em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.6)</label>
</disp-formula>
                    </p>
                    <p>From 
                        <xref ref-type="disp-formula" rid="e10">(3.5)</xref> and 
                        <xref ref-type="disp-formula" rid="e11">(3.6)</xref>, we have ((d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2033;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; (
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2033;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>))(x), &#x2200;x &#x2208; X.</p>
                    <p>Thus &#x201c;&#x2227;&#x201d; is associative. &#x25a0;</p>
                </statement>

                <statement id="state53">
                    <label>Theorem 3.35.</label>
                    <p>L
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X) 
                        <italic toggle="yes">is a semigroup under the binary operation</italic> &#x2227; 
                        <italic toggle="yes">defined by</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x) 
                        <italic toggle="yes">for all</italic> x &#x2208; X
                        <italic toggle="yes">, and</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; L
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X).</p>
                </statement>

                <statement id="state54">
                    <label>Definition 3.36.</label>
                    <p>Let R
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X) be the set of all (r, l)-t-derivations on a PMS-algebra X. Then define a binary operation &#x2227; on R
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X) by (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x), &#x2200;x &#x2208; X, where d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; R
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X).</p>
                </statement>

                <statement id="state55">
                    <label>Lemma 3.37.</label>
                    <p>

                        <italic toggle="yes">If</italic> d
                        <italic toggle="yes">
                            <sub>t</sub> and</italic> d
                        <sup>'</sup>
                        <italic toggle="yes">
                            <sub>t</sub> are</italic> (r, l)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivations on</italic> X
                        <italic toggle="yes">. Then</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) 
                        <italic toggle="yes">is also a</italic> (r, l)
                        <italic toggle="yes">-</italic>t
                        <italic toggle="yes">-derivation on</italic> X.</p>
                </statement>

                <statement id="state56">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; RDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X). For
                        <disp-formula id="e12">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x2208;</mml:mo>
                                            <mml:mi mathvariant="normal">X</mml:mi>
                                            <mml:mo>,</mml:mo>
                                            <mml:mrow>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="13.9em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="13.9em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="13.9em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="13.9em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.7)</label>
</disp-formula>

                        <disp-formula id="e13">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">Y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">y</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi>d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">y</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>y</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>y</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="9.7em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">y</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.8)</label>
</disp-formula>
                    </p>
                    <p>From 
                        <xref ref-type="disp-formula" rid="e12">(3.7)</xref> and 
                        <xref ref-type="disp-formula" rid="e13">(3.8)</xref>, we have, (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x &#x22c6; y) = x &#x22c6; (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(y). &#x25a0;</p>
                </statement>

                <statement id="state57">
                    <label>Lemma 3.38.</label>
                    <p>

                        <italic toggle="yes">The binary operation &#x201c;</italic>&#x2227;
                        <italic toggle="yes">&#x201d; defined on</italic> RDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X) 
                        <italic toggle="yes">is associative.</italic>
                    </p>
                </statement>

                <statement id="state58">
                    <label>

                        <italic toggle="yes">Proof.</italic>
</label>
                    <p>Let d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2033;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; RDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X). Now for, x &#x2208; X.
                        <disp-formula id="e14">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mo>&#x2227;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mo>&#x2227;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mrow>
                                                <mml:mo>=</mml:mo>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                    <mml:mo>&#x22c6;</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                    <mml:mrow>
                                                        <mml:mo stretchy="true">(</mml:mo>
                                                        <mml:mi mathvariant="normal">x</mml:mi>
                                                        <mml:mo stretchy="true">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:msub>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:msub>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mrow>
                                                    <mml:mo stretchy="true">(</mml:mo>
                                                    <mml:mi mathvariant="normal">x</mml:mi>
                                                    <mml:mo stretchy="true">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">X</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>&#x2033;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>&#x2033;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.9)</label>
</disp-formula>And
                        <disp-formula id="e15">

                            <mml:math display="block">
                                <mml:mtable columnalign="left">
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mo>&#x2227;</mml:mo>
                                                    <mml:mo>(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>)</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>=</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:msub>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                    </mml:msub>
                                                    <mml:mo>&#x2227;</mml:mo>
                                                    <mml:mo>(</mml:mo>
                                                    <mml:msubsup>
                                                        <mml:mi mathvariant="normal">d</mml:mi>
                                                        <mml:mi>t</mml:mi>
                                                        <mml:mo>&#x2032;</mml:mo>
                                                    </mml:msubsup>
                                                </mml:mrow>
                                                <mml:mo>&#x2227;</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2033;</mml:mo>
                                                </mml:msubsup>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo>)</mml:mo>
                                            <mml:mrow>
                                                <mml:mo stretchy="true">(</mml:mo>
                                                <mml:mn>0</mml:mn>
                                                <mml:mo>&#x00a0;</mml:mo>
                                                <mml:mo>&#x22c6;</mml:mo>
                                                <mml:mi mathvariant="normal">x</mml:mi>
                                                <mml:mo stretchy="true">)</mml:mo>
                                            </mml:mrow>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mrow>
                                                <mml:mo>(</mml:mo>
                                                <mml:msubsup>
                                                    <mml:mi mathvariant="normal">d</mml:mi>
                                                    <mml:mi>t</mml:mi>
                                                    <mml:mo>&#x2032;</mml:mo>
                                                </mml:msubsup>
                                            </mml:mrow>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo stretchy="true">)</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi mathvariant="normal">d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:mi mathvariant="normal">x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>&#x2032;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mn>0</mml:mn>
                                            <mml:mo>&#x22c6;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2033;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>&#x2033;</mml:mo>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                            <mml:mo>&#x00a0;</mml:mo>
                                            <mml:mo>&#x2227;</mml:mo>
                                            <mml:msubsup>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                                <mml:mo>&#x2032;</mml:mo>
                                            </mml:msubsup>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mtd>
                                            <mml:mspace width="11.8em"/>
                                            <mml:mo>=</mml:mo>
                                            <mml:msub>
                                                <mml:mi>d</mml:mi>
                                                <mml:mi>t</mml:mi>
                                            </mml:msub>
                                            <mml:mo>(</mml:mo>
                                            <mml:mi>x</mml:mi>
                                            <mml:mo>)</mml:mo>
                                        </mml:mtd>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:math>

                            <label>(3.10)</label>
</disp-formula>
                    </p>
                    <p>From 
                        <xref ref-type="disp-formula" rid="e14">(3.9)</xref> and 
                        <xref ref-type="disp-formula" rid="e15">(3.10)</xref>, we have ((d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2033;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; (
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2033;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>))(x), &#x2200;x &#x2208; X. Thus the binary operation &#x201c;&#x2227;&#x201d; is associative on RDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X). &#x25a0;</p>
                </statement>

                <statement id="state59">
                    <label>Theorem 3.39.</label>
                    <p>RDer
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X) 
                        <italic toggle="yes">is a semigroup under the binary operation &#x201c;</italic>&#x2227;
                        <italic toggle="yes">&#x201d; defined by</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x) 
                        <italic toggle="yes">for all</italic> x &#x2208; X
                        <italic toggle="yes">, where</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; R
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>Der(X).</p>
                    <p>Combining 
                        <xref ref-type="statement" rid="state53">Theorem (3.35)</xref> and 
                        <xref ref-type="statement" rid="state59">Theorem (3.39)</xref>, we get the following theorem.</p>
                </statement>

                <statement id="state60">
                    <label>Theorem 3.40.</label>
                    <p>

                        <italic toggle="yes">If</italic> Der
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X) 
                        <italic toggle="yes">denotes the set of all</italic> t
                        <italic toggle="yes">-derivations on</italic> X
                        <italic toggle="yes">. Then it is a semigroup under the binary operation</italic> &#x201c;&#x2227;&#x201d; 
                        <italic toggle="yes">defined by</italic> (d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>)(x) = d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(x) &#x2227; 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula>(x) 
                        <italic toggle="yes">for all</italic> x &#x2208; X
                        <italic toggle="yes">, where</italic> d
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic> 
                        <inline-formula>

                            <mml:math display="inline">
                                <mml:msubsup>
                                    <mml:mi mathvariant="normal">d</mml:mi>
                                    <mml:mi>t</mml:mi>
                                    <mml:mo>&#x2032;</mml:mo>
                                </mml:msubsup>
                            </mml:math>
</inline-formula> &#x2208; Der
                        <italic toggle="yes">
                            <sub>t</sub>
                        </italic>(X).</p>
                </statement>
            </p>
        </sec>
        <sec id="sec8" sec-type="conclusions">
            <title>Conclusions</title>
            <p>The study of propositional logic-based algebraic structures, such as PMS-algebras, is crucial for understanding derivation concepts. Derivations are applied to coding theory. The concept of t-derivations in PMS-algebras is explored, and it is proven that the set of all t-derivations forms a semigroup. This research can be applied to other algebras like BF- algebras, UP-algebras, and KUS-algebras, providing a foundation for further research on derivations.</p>
        </sec>
        <sec id="sec9">
            <title>Ethics and consent</title>
            <p>Ethical approval and consent were not required.</p>
        </sec>
    </body>
    <back>
        <sec id="sec12" sec-type="data-availability">
            <title>Data availability statement</title>
            <p>No data are associated with this article.</p>
        </sec>
        <ack>
            <title>Acknowledgements</title>
            <p>We would like to thank the editor in chief, associate editor, and anonymous reviewers for their valuable comments and suggestions for improving this manuscript.</p>
        </ack>
        <ref-list>
            <title>References</title>
            <ref id="ref1">
                <label>1</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Ganesan</surname>
                            <given-names>P</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Kandaraj</surname>
                            <given-names>N</given-names>
                        </name>
</person-group>:
                    <article-title>A note on t-derivations of BH-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Adv. Appl. Math. Sci.</italic>
</source>
                    <year>2021</year>;<volume>20</volume>(<issue>11</issue>):<fpage>2959</fpage>&#x2013;<lpage>2969</lpage>.</mixed-citation>
            </ref>
            <ref id="ref2">
                <label>2</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Ganeshkumar</surname>
                            <given-names>T</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Chandramouleeswaran</surname>
                            <given-names>M</given-names>
                        </name>
</person-group>:
                    <article-title>t-derivations on TM-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Int. J.Pure Appl. Math.</italic>
</source>
                    <year>2013</year>;<volume>85</volume>(<issue>1</issue>):<fpage>95</fpage>&#x2013;<lpage>107</lpage>.
                    <pub-id pub-id-type="doi">10.12732/ijpam.v85i1.8</pub-id>
                </mixed-citation>
            </ref>
            <ref id="ref3">
                <label>3</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Iseki</surname>
                            <given-names>K</given-names>
                        </name>
</person-group>:
                    <article-title>An introduction to the theory of BCK-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Math. Japon.</italic>
</source>
                    <year>1978</year>;<volume>23</volume>(<issue>1</issue>):<fpage>1</fpage>&#x2013;<lpage>26</lpage>.</mixed-citation>
            </ref>
            <ref id="ref4">
                <label>4</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Iseki</surname>
                            <given-names>K</given-names>
                        </name>
</person-group>:
                    <article-title>On bci-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Math. Seminar Notes.</italic>
</source>
                    <year>1980</year>;<volume>8</volume>:<fpage>235</fpage>&#x2013;<lpage>236</lpage>.</mixed-citation>
            </ref>
            <ref id="ref5">
                <label>5</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Jana</surname>
                            <given-names>C</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Senapati</surname>
                            <given-names>T</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Pal</surname>
                            <given-names>M</given-names>
                        </name>
</person-group>:
                    <article-title>t-derivations on com- plicated subtraction algebras.</article-title>
                    <source>

                        <italic toggle="yes">J. Discret. Math. Sci. Cryptogr.</italic>
</source>
                    <year>2017</year>;<volume>20</volume>(<issue>8</issue>):<fpage>1583</fpage>&#x2013;<lpage>1595</lpage>.
                    <pub-id pub-id-type="doi">10.1080/09720529.2017.1308663</pub-id>
                </mixed-citation>
            </ref>
            <ref id="ref6">
                <label>6</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Javed</surname>
                            <given-names>MA</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Malik</surname>
                            <given-names>SN</given-names>
                        </name>
</person-group>:
                    <article-title>On t-derivations of lattices.</article-title>
                    <source>

                        <italic toggle="yes">Int. J. Contemp. Math. Sci.</italic>
</source>
                    <year>2020</year>;<volume>15</volume>(<issue>4</issue>):<fpage>207</fpage>&#x2013;<lpage>214</lpage>.
                    <pub-id pub-id-type="doi">10.12988/ijcms.2020.91444</pub-id>
                </mixed-citation>
            </ref>
            <ref id="ref7">
                <label>7</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Jun</surname>
                            <given-names>YB</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Xin</surname>
                            <given-names>XL</given-names>
                        </name>
</person-group>:
                    <article-title>On derivations of bci-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Inf. Sci.</italic>
</source>
                    <year>2004</year>;<volume>159</volume>(<issue>3-4</issue>):<fpage>167</fpage>&#x2013;<lpage>176</lpage>.
                    <pub-id pub-id-type="doi">10.1016/j.ins.2003.03.001</pub-id>
                </mixed-citation>
            </ref>
            <ref id="ref8">
                <label>8</label>
                <mixed-citation publication-type="other">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Megalai</surname>
                            <given-names>K</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Tamilarasi</surname>
                            <given-names>A</given-names>
                        </name>
</person-group>:
                    <article-title>Classification of TM-algebra, IJCA Special Issue on &#x201c;Computer Aided Soft Computing Techniques for Imaging and Biomedical Applications&#x201d; CASCT.</article-title>
                    <year>2010</year>.</mixed-citation>
            </ref>
            <ref id="ref9">
                <label>9</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Mostafa</surname>
                            <given-names>SM</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Abdel Naby</surname>
                            <given-names>MA</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Abdel Halim</surname>
                            <given-names>F</given-names>
                        </name>

                        <etal/>
</person-group>:
                    <article-title>On KUS-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Int. J. Algebra.</italic>
</source>
                    <year>2013</year>;<volume>7</volume>(<issue>3</issue>):<fpage>131</fpage>&#x2013;<lpage>144</lpage>.
                    <pub-id pub-id-type="doi">10.12988/ija.2013.13013</pub-id>
                </mixed-citation>
            </ref>
            <ref id="ref10">
                <label>10</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Muhiuddin</surname>
                            <given-names>G</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Abdullah Al-roqi</surname>
                            <given-names>M</given-names>
                        </name>
</person-group>:
                    <article-title>On t-Derivations of BCI-Algebras.</article-title>
                    <source>

                        <italic toggle="yes">Abstr. Appl. Anal.</italic>
</source>
                    <year>2012</year>;<volume>2012</volume>:<fpage>Article ID 872784</fpage>.
                    <pub-id pub-id-type="doi">10.1155/2012/872784</pub-id>
                </mixed-citation>
            </ref>
            <ref id="ref11">
                <label>11</label>
                <mixed-citation publication-type="other">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Sithar Selvam</surname>
                            <given-names>PM</given-names>
                        </name>

                        <name name-style="western">
                            <surname>Nagalakshmi</surname>
                            <given-names>KT</given-names>
                        </name>
</person-group>:
                    <article-title>On PMS-algebras, Transylvanian Review.</article-title>
                    <year>2016</year>;<volume>24</volume>(<issue>10</issue>):<fpage>1622</fpage>&#x2013;<lpage>1628</lpage>.</mixed-citation>
            </ref>
            <ref id="ref12">
                <label>12</label>
                <mixed-citation publication-type="journal">
                    <person-group person-group-type="author">

                        <name name-style="western">
                            <surname>Siswanti</surname>
                            <given-names>FT</given-names>
                        </name>
</person-group>:
                    <article-title>Sri Gemawati, and Syamsudhuha Syamsudhuha, t-derivations in BP-algebras.</article-title>
                    <source>

                        <italic toggle="yes">Sci. Technol. Commun. J.</italic>
</source>
                    <year>2021</year>;<volume>1</volume>(<issue>3</issue>):<fpage>97</fpage>&#x2013;<lpage>103</lpage>.
                    <pub-id pub-id-type="doi">10.59190/stc.v1i3.199</pub-id>
                </mixed-citation>
            </ref>
        </ref-list>
    </back>
    <sub-article article-type="reviewer-report" id="report375060">
        <front-stub>
            <article-id pub-id-type="doi">10.5256/f1000research.175478.r375060</article-id>
            <title-group>
                <article-title>Reviewer response for version 1</article-title>
            </title-group>
            <contrib-group>
                <contrib contrib-type="author">
                    <name>
                        <surname>P</surname>
                        <given-names>Hemavathi</given-names>
                    </name>
                    <xref ref-type="aff" rid="r375060a2">2</xref>
                    <role>Referee</role>
                    <uri content-type="orcid">https://orcid.org/0000-0003-0607-2817</uri>
                </contrib>
                <contrib contrib-type="author">
                    <name>
                        <surname>R</surname>
                        <given-names>Dr. Vinod Kumar</given-names>
                    </name>
                    <xref ref-type="aff" rid="r375060a1">1</xref>
                    <role>Co-referee</role>
                </contrib>
                <aff id="r375060a1">
                    <label>1</label>Mathematics, Rajalakshmi Engineering College, Thandalam/Chennai, Tamil Nadu, India</aff>
                <aff id="r375060a2">
                    <label>2</label>Saveetha Institute of Medical and Technical Sciences (SIMATS), Thandalam, India</aff>
            </contrib-group>
            <author-notes>
                <fn fn-type="conflict">
                    <p>
                        <bold>Competing interests: </bold>No competing interests were disclosed.</p>
                </fn>
            </author-notes>
            <pub-date pub-type="epub">
                <day>28</day>
                <month>6</month>
                <year>2025</year>
            </pub-date>
            <permissions>
                <copyright-statement>Copyright: &#x00a9; 2025 R DVK and P H</copyright-statement>
                <copyright-year>2025</copyright-year>
                <license xlink:href="https://creativecommons.org/licenses/by/4.0/">
                    <license-p>This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</license-p>
                </license>
            </permissions>
            <related-article ext-link-type="doi" id="relatedArticleReport375060" related-article-type="peer-reviewed-article" xlink:href="10.12688/f1000research.159711.1"/>
            <custom-meta-group>
                <custom-meta>
                    <meta-name>recommendation</meta-name>
                    <meta-value>approve</meta-value>
                </custom-meta>
            </custom-meta-group>
        </front-stub>
        <body>
            <p>The manuscript presents a rigorous and comprehensive study of t-derivations in PMS-algebras, an emerging algebraic framework that generalizes several known systems such as BCK-, BCI-, TM-, and KUS-algebras. The paper introduces and explores both left-right and right-left t-derivations, regular t-derivations, and their algebraic behavior within PMS-algebras, culminating in the significant result that the set of all t-derivations forms a semigroup.</p>
            <p> </p>
            <p> 
                <bold>Strengths</bold> 
                <list list-type="bullet">
                    <list-item>
                        <p>The topic is mathematically 
                            <bold>relevant and original</bold>, expanding derivation concepts to a broader class of algebraic systems.</p>
                    </list-item>
                    <list-item>
                        <p>The 
                            <bold>definitions are precise</bold>, and the theorems are stated clearly with logically consistent proofs.</p>
                    </list-item>
                    <list-item>
                        <p>The paper is well-structured, gradually developing the theory with 
                            <bold>examples and counterexamples</bold> to support understanding.</p>
                    </list-item>
                    <list-item>
                        <p>The establishment of 
                            <bold>semigroup properties</bold> for derivation mappings is a valuable algebraic contribution.</p>
                    </list-item>
                </list> 
                <bold>Concerns and Suggestions</bold> 
                <list list-type="order">
                    <list-item>
                        <p>While the paper is mathematically sound, some 
                            <bold>phrases are awkwardly constructed</bold>, which may affect reader comprehension. A 
                            <bold>language refinement</bold> or minor copy-editing is recommended to improve clarity (e.g., consistent use of &#x201c;self-map&#x201d;, &#x201c;identity map&#x201d;, etc.).</p>
                    </list-item>
                    <list-item>
                        <p>veral notations such as dt, d&#x2019;t, &#x2227;, and various operation compositions (&#x25e6;, &#x22c6;) are heavily reused. A 
                            <bold>notation table</bold> at the beginning or end would be helpful for reference.</p>
                    </list-item>
                    <list-item>
                        <p>The introduction could be strengthened by briefly discussing 
                            <bold>potential applications or motivations</bold> for studying derivations in PMS-algebras, especially in logic, coding theory, or information systems, as hinted in the conclusion.</p>
                    </list-item>
                </list> 
                <bold>Minor Comments</bold> 
                <list list-type="bullet">
                    <list-item>
                        <p>Fix typographical issues (e.g., &#x201c;regualr&#x201d; &#x2192; &#x201c;regular&#x201d;; inconsistent capitalizations in definitions and remarks).</p>
                    </list-item>
                    <list-item>
                        <p>The references are appropriate but could benefit from 
                            <bold>standardized formatting</bold> for better consistency (some include first names; others don&#x2019;t).</p>
                    </list-item>
                </list> Consider revising the 
                <bold>abstract</bold> to be more informative currently, it repeats &#x201c;we study&#x201d; and &#x201c;we prove&#x201d; without summarizing the key findings in a concise, technical tone.</p>
            <p> </p>
            <p> 
                <bold>Recommendation:</bold>
            </p>
            <p> 
                <bold>Minor Revision</bold>
            </p>
            <p> The manuscript provides a well-structured and significant contribution to algebraic logic and derivation theory. A minor revision focusing on language, presentation, and notational clarity will enhance the paper&#x2019;s accessibility and impact.</p>
            <p>Is the work clearly and accurately presented and does it cite the current literature?</p>
            <p>Yes</p>
            <p>If applicable, is the statistical analysis and its interpretation appropriate?</p>
            <p>Not applicable</p>
            <p>Are all the source data underlying the results available to ensure full reproducibility?</p>
            <p>No source data required</p>
            <p>Is the study design appropriate and is the work technically sound?</p>
            <p>Yes</p>
            <p>Are the conclusions drawn adequately supported by the results?</p>
            <p>Yes</p>
            <p>Are sufficient details of methods and analysis provided to allow replication by others?</p>
            <p>Yes</p>
            <p>Reviewer Expertise:</p>
            <p>Fuzzy algebra, Fuzzy Decision Making, Neutrosophic Sets</p>
            <p>We confirm that we have read this submission and believe that we have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.</p>
        </body>
        <sub-article article-type="response" id="comment14170-375060">
            <front-stub>
                <contrib-group>
                    <contrib contrib-type="author">
                        <name>
                            <surname>Melese Kassahun</surname>
                            <given-names>Nibret</given-names>
                        </name>
                        <aff>Mathematics, Bahir Dar University College of Science, Bahir Dar, Amhara, Ethiopia</aff>
                    </contrib>
                </contrib-group>
                <author-notes>
                    <fn fn-type="conflict">
                        <p>
                            <bold>Competing interests: </bold>No competing interests were disclosed.</p>
                    </fn>
                </author-notes>
                <pub-date pub-type="epub">
                    <day>28</day>
                    <month>6</month>
                    <year>2025</year>
                </pub-date>
            </front-stub>
            <body>
                <p>We have accepted the reviewers' comments and thank you for the valuable feedback.</p>
                <p> </p>
                <p> Thank you,</p>
                <p> Dr. Nibret Melese Kassahun</p>
                <p> Corresponding author of the article.</p>
            </body>
        </sub-article>
    </sub-article>
    <sub-article article-type="reviewer-report" id="report375059">
        <front-stub>
            <article-id pub-id-type="doi">10.5256/f1000research.175478.r375059</article-id>
            <title-group>
                <article-title>Reviewer response for version 1</article-title>
            </title-group>
            <contrib-group>
                <contrib contrib-type="author">
                    <name>
                        <surname>Yedlapalli</surname>
                        <given-names>Phani</given-names>
                    </name>
                    <xref ref-type="aff" rid="r375059a1">1</xref>
                    <role>Referee</role>
                </contrib>
                <aff id="r375059a1">
                    <label>1</label>Shri Vishnu Engineering College for Women, Vishnupur, India</aff>
            </contrib-group>
            <author-notes>
                <fn fn-type="conflict">
                    <p>
                        <bold>Competing interests: </bold>No competing interests were disclosed.</p>
                </fn>
            </author-notes>
            <pub-date pub-type="epub">
                <day>26</day>
                <month>5</month>
                <year>2025</year>
            </pub-date>
            <permissions>
                <copyright-statement>Copyright: &#x00a9; 2025 Yedlapalli P</copyright-statement>
                <copyright-year>2025</copyright-year>
                <license xlink:href="https://creativecommons.org/licenses/by/4.0/">
                    <license-p>This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</license-p>
                </license>
            </permissions>
            <related-article ext-link-type="doi" id="relatedArticleReport375059" related-article-type="peer-reviewed-article" xlink:href="10.12688/f1000research.159711.1"/>
            <custom-meta-group>
                <custom-meta>
                    <meta-name>recommendation</meta-name>
                    <meta-value>approve</meta-value>
                </custom-meta>
            </custom-meta-group>
        </front-stub>
        <body>
            <p>The paper presents a novel study on 
                <italic>t-derivations</italic> and 
                <italic>regular derivations</italic> in PMS-algebras, introducing&#x00a0; concepts with mathematical rigor. The authors successfully explore key properties of these derivations, grounded in the structural framework of PMS-algebras. A notable result is that the set of all t-derivations forms a semigroup, which adds depth to the algebraic structure. The work is original, clearly written, and logically organized. The results have potential for further exploration and applications. Overall, this is a valuable and publishable contribution to algebraic research.</p>
            <p>Is the work clearly and accurately presented and does it cite the current literature?</p>
            <p>Yes</p>
            <p>If applicable, is the statistical analysis and its interpretation appropriate?</p>
            <p>Yes</p>
            <p>Are all the source data underlying the results available to ensure full reproducibility?</p>
            <p>Yes</p>
            <p>Is the study design appropriate and is the work technically sound?</p>
            <p>Yes</p>
            <p>Are the conclusions drawn adequately supported by the results?</p>
            <p>Yes</p>
            <p>Are sufficient details of methods and analysis provided to allow replication by others?</p>
            <p>Yes</p>
            <p>Reviewer Expertise:</p>
            <p>Algebras</p>
            <p>I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.</p>
        </body>
        <sub-article article-type="response" id="comment13956-375059">
            <front-stub>
                <contrib-group>
                    <contrib contrib-type="author">
                        <name>
                            <surname>Melese Kassahun</surname>
                            <given-names>Nibret</given-names>
                        </name>
                        <aff>Mathematics, Bahir Dar University College of Science, Bahir Dar, Amhara, Ethiopia</aff>
                    </contrib>
                </contrib-group>
                <author-notes>
                    <fn fn-type="conflict">
                        <p>
                            <bold>Competing interests: </bold>No competing interests were disclosed.</p>
                    </fn>
                </author-notes>
                <pub-date pub-type="epub">
                    <day>26</day>
                    <month>5</month>
                    <year>2025</year>
                </pub-date>
            </front-stub>
            <body>
                <p>We have read the comments made by the reviewer and we have been accept all of the valuable comments which are constructive.</p>
                <p> Thank you for your valid comments &#x00a0;</p>
                <p> Nibret Melese kassahun</p>
            </body>
        </sub-article>
    </sub-article>
</article>
