<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">OJMSi</journal-id><journal-title-group><journal-title>Open Journal of Modelling and Simulation</journal-title></journal-title-group><issn pub-type="epub">2327-4018</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/ojmsi.2015.33007</article-id><article-id pub-id-type="publisher-id">OJMSi-56936</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Physics&amp;Mathematics</subject></subj-group></article-categories><title-group><article-title>
 
 
  Some New Results on the Number of Paths
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>eih</surname><given-names>S. El-Desouky</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Abdelfattah</surname><given-names>Mustafa</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>E.</surname><given-names>M. Mahmoud</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib></contrib-group><aff id="aff2"><addr-line>Mathematics Department, Faculty of Science, Aswan University, Aswan, Egypt</addr-line></aff><aff id="aff1"><addr-line>Mathematics Department, Faculty of Science, Mansoura University, Mansoura, Egypt</addr-line></aff><author-notes><corresp id="cor1">* E-mail:<email>b_desouky@yahoo.com(ESE)</email>;<email>abdelfatah_mustafa@yahoo.com(AM)</email>;</corresp></author-notes><pub-date pub-type="epub"><day>05</day><month>06</month><year>2015</year></pub-date><volume>03</volume><issue>03</issue><fpage>63</fpage><lpage>69</lpage><history><date date-type="received"><day>23</day>	<month>April</month>	<year>2015</year></date><date date-type="rev-recd"><day>accepted</day>	<month>1</month>	<year>June</year>	</date><date date-type="accepted"><day>5</day>	<month>June</month>	<year>2015</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  Khidr and El-Desouky [1] derived a symmetric sum involving the Stirling numbers of the first kind through the process of counting the number of paths along a rectangular array 
  <em>n</em>*
  <em>m</em> denoted by 
  <em> A</em>
  <sub><em>nm</em></sub>. We investigate the generating function for the general case and hence some special cases as well. The probability function of the number of paths along is obtained. Moreover, the moment generating function of the random variable X and hence the mean and variance are obtained. Finally, some applications are introduced.
 
</p></abstract><kwd-group><kwd>Stirling Numbers</kwd><kwd> Generating Function</kwd><kwd> Moment Generating Function</kwd><kwd> Comtet Numbers</kwd><kwd> Maple Program</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>Let <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x8.png" xlink:type="simple"/></inline-formula> be a sequence of natural numbers<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x9.png" xlink:type="simple"/></inline-formula>, and <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x10.png" xlink:type="simple"/></inline-formula> be an <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x11.png" xlink:type="simple"/></inline-formula> array associated with this sequence, whose entries <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x12.png" xlink:type="simple"/></inline-formula> such that</p><disp-formula id="scirp.56936-formula74"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x13.png"  xlink:type="simple"/></disp-formula><p>The path of order k along <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x14.png" xlink:type="simple"/></inline-formula> is defined to be a sequence of entries <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x15.png" xlink:type="simple"/></inline-formula> as follows</p><disp-formula id="scirp.56936-formula75"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x16.png"  xlink:type="simple"/></disp-formula><p>The number of paths of order k will be denoted by</p><disp-formula id="scirp.56936-formula76"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x17.png"  xlink:type="simple"/></disp-formula><p>By neglecting the last row in <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x18.png" xlink:type="simple"/></inline-formula> and then reconsidering it, we get the recurrence</p><disp-formula id="scirp.56936-formula77"><label>(1)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x19.png"  xlink:type="simple"/></disp-formula><p>When<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x20.png" xlink:type="simple"/></inline-formula>, a is a constant, <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x20.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x21.png" xlink:type="simple"/></inline-formula>then</p><disp-formula id="scirp.56936-formula78"><label>(2)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x22.png"  xlink:type="simple"/></disp-formula><p>and</p><disp-formula id="scirp.56936-formula79"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x23.png"  xlink:type="simple"/></disp-formula><p>Khidr and El-Desouky [<xref ref-type="bibr" rid="scirp.56936-ref1">1</xref>] proved that, when <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x24.png" xlink:type="simple"/></inline-formula></p><disp-formula id="scirp.56936-formula80"><label>(3)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x25.png"  xlink:type="simple"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x26.png" xlink:type="simple"/></inline-formula> are the generalized Stirling numbers of the first kind associated with the sequence of real numbers<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x26.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x27.png" xlink:type="simple"/></inline-formula>, defined by [<xref ref-type="bibr" rid="scirp.56936-ref1">1</xref>] - [<xref ref-type="bibr" rid="scirp.56936-ref6">6</xref>] ,</p><disp-formula id="scirp.56936-formula81"><label>(4)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x28.png"  xlink:type="simple"/></disp-formula><p>These numbers satisfy the recurrence relation</p><disp-formula id="scirp.56936-formula82"><label>(5)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x29.png"  xlink:type="simple"/></disp-formula><p>And</p><disp-formula id="scirp.56936-formula83"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x30.png"  xlink:type="simple"/></disp-formula><p>Moreover, they introduced a special case of (3), when<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x31.png" xlink:type="simple"/></inline-formula>, then the number of paths of order k, <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x31.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x32.png" xlink:type="simple"/></inline-formula>is denoted by<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x31.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x32.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x33.png" xlink:type="simple"/></inline-formula>; and proved that</p><disp-formula id="scirp.56936-formula84"><label>(6)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x34.png"  xlink:type="simple"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x35.png" xlink:type="simple"/></inline-formula> are the Stirling numbers of the first kind defined by, see [<xref ref-type="bibr" rid="scirp.56936-ref2">2</xref>] [<xref ref-type="bibr" rid="scirp.56936-ref3">3</xref>]</p><disp-formula id="scirp.56936-formula85"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x36.png"  xlink:type="simple"/></disp-formula><p>Also the generating function for <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x37.png" xlink:type="simple"/></inline-formula> is given by</p><disp-formula id="scirp.56936-formula86"><label>(7)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x38.png"  xlink:type="simple"/></disp-formula><p>In this article, in Section 2, we derive a generalization of some results given in [<xref ref-type="bibr" rid="scirp.56936-ref1">1</xref>] , for the number of paths of</p><p>order k, <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x39.png" xlink:type="simple"/></inline-formula>, when<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x39.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x40.png" xlink:type="simple"/></inline-formula>. The generating function of <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x39.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x40.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x41.png" xlink:type="simple"/></inline-formula> is given. In Section 3, we find the probability distribution for <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x39.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x40.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x41.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x42.png" xlink:type="simple"/></inline-formula> and study some of their properties. The moment</p><p>generating function, skewness and kurtosis for <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x43.png" xlink:type="simple"/></inline-formula> are investigated. Moreover special case and numerical results are given in Section 4.</p></sec><sec id="s2"><title>2. Main Results</title><p>Theorem 1. The number of paths of order k is given by</p><disp-formula id="scirp.56936-formula87"><label>(8)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x44.png"  xlink:type="simple"/></disp-formula><p>Proof. Using (5) in (8), we get</p><disp-formula id="scirp.56936-formula88"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x45.png"  xlink:type="simple"/></disp-formula><p>This by virtue of (1) completes the proof of (8).</p><p>Theorem 2. The generating function of the number of paths of order k is given by</p><disp-formula id="scirp.56936-formula89"><label>(9)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x46.png"  xlink:type="simple"/></disp-formula><p>Proof. Let the generating function of the number of paths of order k be denoted by</p><disp-formula id="scirp.56936-formula90"><label>(10)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x47.png"  xlink:type="simple"/></disp-formula><p>Using (1), we obtain</p><disp-formula id="scirp.56936-formula91"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x48.png"  xlink:type="simple"/></disp-formula><p>and hence we get</p><disp-formula id="scirp.56936-formula92"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x49.png"  xlink:type="simple"/></disp-formula><p>where<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x50.png" xlink:type="simple"/></inline-formula>. This completes the proof.</p><p>From (9), we get</p><disp-formula id="scirp.56936-formula93"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x51.png"  xlink:type="simple"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x52.png" xlink:type="simple"/></inline-formula> and hence we have</p><disp-formula id="scirp.56936-formula94"><label>(11)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x53.png"  xlink:type="simple"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x54.png" xlink:type="simple"/></inline-formula></p><p>For the special case<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x55.png" xlink:type="simple"/></inline-formula>, we get</p><disp-formula id="scirp.56936-formula95"><label>(12)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x56.png"  xlink:type="simple"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x57.png" xlink:type="simple"/></inline-formula></p><p>From (6) and (12), we have the identity</p><disp-formula id="scirp.56936-formula96"><label>(13)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x58.png"  xlink:type="simple"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x59.png" xlink:type="simple"/></inline-formula></p></sec><sec id="s3"><title>3. Some Applications</title><p>Let X, be the number of paths along<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x60.png" xlink:type="simple"/></inline-formula>, then by virtue of (8) we have</p><disp-formula id="scirp.56936-formula97"><label>(14)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x61.png"  xlink:type="simple"/></disp-formula><p>On the other hand the moment generating function of the random variable X denoted by<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x62.png" xlink:type="simple"/></inline-formula>, is given by the following theorem.</p><p>Theorem 3. The moment generating function of X, is given by</p><disp-formula id="scirp.56936-formula98"><label>(15)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x63.png"  xlink:type="simple"/></disp-formula><p>Proof. We begin by the definition of the moment generating function as follows.</p><disp-formula id="scirp.56936-formula99"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x64.png"  xlink:type="simple"/></disp-formula><p>This completes the proof.</p><p>Corollary 1. The jth moments of X is</p><disp-formula id="scirp.56936-formula100"><label>(16)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x65.png"  xlink:type="simple"/></disp-formula><p>Proof. The jth moments can be obtained from the moment generating function, <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x66.png" xlink:type="simple"/></inline-formula>where</p><disp-formula id="scirp.56936-formula101"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x67.png"  xlink:type="simple"/></disp-formula><p>This completes the proof.</p><p>Then from (16), we can calculate the mean and variance for the random variable X as follows.</p><disp-formula id="scirp.56936-formula102"><label>(17)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x68.png"  xlink:type="simple"/></disp-formula><disp-formula id="scirp.56936-formula103"><label>(18)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x69.png"  xlink:type="simple"/></disp-formula><p>hence the variance is given by</p><disp-formula id="scirp.56936-formula104"><label>(19)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x70.png"  xlink:type="simple"/></disp-formula><p>Corollary 2. The Skewness and kurtosis for the random variable X are given by</p><disp-formula id="scirp.56936-formula105"><label>(20)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x71.png"  xlink:type="simple"/></disp-formula><p>where</p><disp-formula id="scirp.56936-formula106"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x72.png"  xlink:type="simple"/></disp-formula><disp-formula id="scirp.56936-formula107"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x73.png"  xlink:type="simple"/></disp-formula><disp-formula id="scirp.56936-formula108"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x74.png"  xlink:type="simple"/></disp-formula><p>Proof. We can find the jth moments about the mean by using</p><disp-formula id="scirp.56936-formula109"><label>(21)</label><graphic position="anchor" xlink:href="http://html.scirp.org/file/1-2860056x75.png"  xlink:type="simple"/></disp-formula><p>From (16) and (21), we can find the moments <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x76.png" xlink:type="simple"/></inline-formula> about mean which can be used to calculate the skweness and kurtosis.</p><p>Special Case:</p><p>If<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x77.png" xlink:type="simple"/></inline-formula>, from (14), we have</p><disp-formula id="scirp.56936-formula110"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x78.png"  xlink:type="simple"/></disp-formula><p>and from (16) the jth moments has the form</p><disp-formula id="scirp.56936-formula111"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x79.png"  xlink:type="simple"/></disp-formula><p>and the mean is given by</p><disp-formula id="scirp.56936-formula112"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x80.png"  xlink:type="simple"/></disp-formula><disp-formula id="scirp.56936-formula113"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x81.png"  xlink:type="simple"/></disp-formula><p>the variance can be obtained as follows.</p><disp-formula id="scirp.56936-formula114"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x82.png"  xlink:type="simple"/></disp-formula><p>where we used<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x83.png" xlink:type="simple"/></inline-formula>, see [<xref ref-type="bibr" rid="scirp.56936-ref3">3</xref>] .</p></sec><sec id="s4"><title>4. Numerical Results</title><p>Setting<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x84.png" xlink:type="simple"/></inline-formula>. Therefore the numerical values of<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x84.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x85.png" xlink:type="simple"/></inline-formula>, are reduced to<inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x84.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x85.png" xlink:type="simple"/></inline-formula><inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x86.png" xlink:type="simple"/></inline-formula>, see [<xref ref-type="bibr" rid="scirp.56936-ref4">4</xref>] [<xref ref-type="bibr" rid="scirp.56936-ref5">5</xref>] .</p><p>From Equation (14), we can find the probability distribution of the number of paths X along <inline-formula><inline-graphic xlink:href="http://html.scirp.org/file/1-2860056x87.png" xlink:type="simple"/></inline-formula> as follows</p><p>From (16), we can compute the 4th moments as follows.</p><p>The 4<sup>th</sup> moments about mean can be obtained as</p><p>The values of mean and variance can be obtained from (17) and (19) as follows.</p><disp-formula id="scirp.56936-formula115"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x90.png"  xlink:type="simple"/></disp-formula><p>The skewness and kurtosis, respectively can be obtained from (20) as follows.</p><disp-formula id="scirp.56936-formula116"><graphic  xlink:href="http://html.scirp.org/file/1-2860056x91.png"  xlink:type="simple"/></disp-formula></sec></body><back><ref-list><title>References</title><ref id="scirp.56936-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">Khidr, A.M. and El-Desouky, B.S. 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Reidel Publishing Company, Dordrecht, Holand.</mixed-citation></ref><ref id="scirp.56936-ref4"><label>4</label><mixed-citation publication-type="journal" xlink:type="simple"><name name-style="western"><surname>El-Desouky</surname><given-names> B.S. </given-names></name>,<etal>et al</etal>. (<year>1994</year>)<article-title>Multiparameter Non-Central Stirling Numbers</article-title><source> The Fibonacci Quarterly</source><volume> 32</volume>,<fpage> 218</fpage>-<lpage>225</lpage>.<pub-id pub-id-type="doi"></pub-id></mixed-citation></ref><ref id="scirp.56936-ref5"><label>5</label><mixed-citation publication-type="other" xlink:type="simple">El-Desouky, B.S. and Cakic, N.P. (2011) Generalized Higher Order Stirling Numbers. Mathematical and Computer Modelling, 54, 2848-2857. http://dx.doi.org/10.1016/j.mcm.2011.07.005</mixed-citation></ref><ref id="scirp.56936-ref6"><label>6</label><mixed-citation publication-type="other" xlink:type="simple">Cakic, N.P., El-Desouky, B.S. and Milovanovic, G.V. (2013) Explicit Formulas and Combinatorial Identities for Generalized Stirling Numbers. Mediterranean Journal of Mathematics, 10, 57-72.  
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