<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1409-2433</journal-id>
<journal-title><![CDATA[Revista de Matemática Teoría y Aplicaciones]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. Mat]]></abbrev-journal-title>
<issn>1409-2433</issn>
<publisher>
<publisher-name><![CDATA[Centro de Investigaciones en Matemática Pura y Aplicada (CIMPA) y Escuela de Matemática, San José, Costa Rica.]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1409-24332013000200008</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Algoritmo de búsqueda tabú para una variante del problema de coloración]]></article-title>
<article-title xml:lang="en"><![CDATA[Tabu search algorithm for a variation of the coloring problem]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Aboytes-Ojeda]]></surname>
<given-names><![CDATA[Mario]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Laureano-Cruces]]></surname>
<given-names><![CDATA[Ana Lilia]]></given-names>
</name>
<xref ref-type="aff" rid="A02"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Ramírez-Rodríguez]]></surname>
<given-names><![CDATA[Javier]]></given-names>
</name>
<xref ref-type="aff" rid="A03"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Nacional Autónoma de México  ]]></institution>
<addr-line><![CDATA[ México D.F.]]></addr-line>
<country>México</country>
</aff>
<aff id="A02">
<institution><![CDATA[,Universidad Autónoma Metropolitana Departamento de Sistemas ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>France</country>
</aff>
<aff id="A03">
<institution><![CDATA[,Universidad Autónoma Metroplitana Laboratoire d&#8217;Informatique d&#8217;Avignon ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2013</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2013</year>
</pub-date>
<volume>20</volume>
<numero>2</numero>
<fpage>215</fpage>
<lpage>230</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S1409-24332013000200008&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S1409-24332013000200008&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S1409-24332013000200008&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[El problema de coloración robusta generalizado (PCRG) resuelve problemas de horarios que consideran restricciones especiales. Al ser una generalización del problema de coloración robusta, que es a su vez una generalización del problema de coloración, el PCRG es entonces un problema NP-Completo, por lo que es necesario utilizar métodos aproximados para encontrar buenas soluciones en un tiempo de cómputo razonable. En este trabajo se presenta un algoritmo de búsqueda tabú para programar casos de 30 a 180 horas por semana, para algunos de ellos encuentra la solución ´optima, en otros casos, la solución obtenida supera a la mejor solución conocida. También se presentan ejemplos de mayor tamaño a los conocidos, obteniendo resultados muy competitivos, lo que se puede verificar por la ausencia de conflicto entre clases.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[The generalized robust coloring problem (GRCP) resolves timetabling problems that consider special constraints. As a generalization of the robust coloring problem, which is in turn a generalization of the coloring problem, the GRCP is then a NP-Complete problem, so it is necessary to use approximate methods to find good solutions in a reasonable computation time. This paper presents a tabu search algorithm to schedule cases from 30 to 180 hours per week, for some of them it found the optimal solution, in other cases, the solution obtained exceeds the best known solution. It also presents examples of greater size to the known, obtaining very competitive results, which can be verified by the absence of class conflict.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[coloración robusta]]></kwd>
<kwd lng="es"><![CDATA[problemas de horarios]]></kwd>
<kwd lng="es"><![CDATA[heurísticas]]></kwd>
<kwd lng="en"><![CDATA[robust coloring]]></kwd>
<kwd lng="en"><![CDATA[timetabling problems]]></kwd>
<kwd lng="en"><![CDATA[heuristics]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <div style="text-align: justify;">     <div style="text-align: justify;">     <div style="text-align: center;"><font style="font-weight: bold;"  size="4"><span style="font-family: verdana;">Algoritmo de b&uacute;squeda tab&uacute; para una variante del problema de coloraci&oacute;n</span></font><br  style="font-family: verdana; font-weight: bold;"> <br style="font-family: verdana; font-weight: bold;"> <font style="font-weight: bold;" size="4"><span  style="font-family: verdana;">Tabu search algorithm for a variation of the coloring problem</span></font><br  style="font-family: verdana;"> </div> <br style="font-family: verdana;">     <div style="font-family: verdana; text-align: center;"><font size="2">Mario Aboytes&#8211;Ojeda<sup><a href="#1">*</a><a name="4"></a>+</sup>, Ana Lilia Laureano&#8211;Cruces<sup><a href="#2">&#8224;</a><a name="5"></a>+</sup>, Javier Ram&iacute;rez&#8211;Rodr&iacute;guez<sup><a href="#3">&#8225;</a><a name="6"></a>+</sup></font>    <br> </div> <font size="2"><span style="font-family: verdana;"><br  style="font-family: verdana;"> </span></font><small><span style="font-family: verdana;"><a  name="Correspondencia2"></a>*<a href="#correspondencia">Direcci&oacute;n para correspondencia:</a></span></small><br style="font-family: verdana;"> <hr style="width: 100%; height: 2px;"><font size="3"><span  style="font-family: verdana; font-weight: bold;">Resumen</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">El problema de coloraci&oacute;n robusta generalizado (PCRG) resuelve problemas de horarios que consideran restricciones especiales. Al ser una generalizaci&oacute;n del problema de coloraci&oacute;n robusta, que es a su vez una generalizaci&oacute;n del problema de coloraci&oacute;n, el PCRG es entonces un problema NP-Completo, por lo que es necesario utilizar m&eacute;todos aproximados para encontrar buenas soluciones en un tiempo de c&oacute;mputo razonable. En este trabajo se presenta un algoritmo de b&uacute;squeda tab&uacute; para programar casos de 30 a 180 horas por semana, para algunos de ellos encuentra la soluci&oacute;n &acute;optima, en otros casos, la soluci&oacute;n obtenida supera a la mejor soluci&oacute;n conocida. Tambi&eacute;n se presentan ejemplos de mayor tama&ntilde;o a los conocidos, obteniendo resultados muy competitivos, lo que se puede verificar por la ausencia de conflicto entre clases.</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;"><span  style="font-weight: bold;">Palabras clave:</span> coloraci&oacute;n robusta, problemas de horarios, heur&iacute;sticas.</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="3"><span style="font-family: verdana; font-weight: bold;">Abstract</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">The generalized robust coloring problem (GRCP) resolves timetabling problems that consider special constraints. As a generalization of the robust coloring problem, which is in turn a generalization of the coloring problem, the GRCP is then a NP-Complete problem, so it is necessary to use approximate methods to find good solutions in a reasonable computation time. This paper presents a tabu search algorithm to schedule cases from 30 to 180 hours per week, for some of them it found the optimal solution, in other cases, the solution obtained exceeds the best known solution. It also presents</span></font><br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">examples of greater size to the known, obtaining very competitive results, which can be verified by the absence of class conflict. </span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;"><span  style="font-weight: bold;">Keywords:</span> robust coloring, timetabling problems, heuristics. </span></font><br  style="font-family: verdana;"> <br style="font-family: verdana; font-weight: bold;"> <font size="2"><span style="font-family: verdana;"><span  style="font-weight: bold;">Mathematics Subject Classification:</span> 05C15, 90C59, 68T20.    <br> </span></font> <hr style="width: 100%; height: 2px;"><font size="2"><span  style="font-family: verdana;">    <br> </span></font><span  style="color: rgb(0, 0, 0); font-family: verdana; font-size: small; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: justify; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; background-color: rgb(255, 255, 255); display: inline ! important; float: none;">Ver contenido disponible en pdf    <br> <br style="font-family: verdana;"> </span> <hr style="width: 100%; height: 2px;">    <!-- ref --><br> <font size="3"><span style="font-family: verdana; font-weight: bold;">Referencias</span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[1] Alvarez Vald&eacute;z, R.; Crespo, E.; Tamarit, J.M. (1997) &#8220;A tabu search algorithm to schedule university examinations&#8221;, Q&uuml;estio&oacute; 21(1 &amp; 2): 201&#8211;215.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957647&pid=S1409-2433201300020000800001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><br> <br style="font-family: verdana;"> </span></font><font size="2"><span style="font-family: verdana;">[2] de Werra, D. (1995) &#8220;Some combinatorial models for course scheduling&#8221;, <span  style="font-style: italic;">PATAT&#8217;95</span>: 296&#8211;308.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957648&pid=S1409-2433201300020000800002&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[3] de Werra, D. (1996) &#8220;An introduction to timetabling&#8221;, <span style="font-style: italic;">Lecture Notes in Computer Science</span> 1153, Springer: 296&#8211;308.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957649&pid=S1409-2433201300020000800003&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[4] Glover, F. (1989) &#8220;Tabu search - Part I&#8221;, <span style="font-style: italic;">INFORMS Journal on Computing</span> 1: 190&#8211;206.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957650&pid=S1409-2433201300020000800004&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[5] Glover, F.; Laguna, M. (1997) <span style="font-style: italic;">Tabu search</span>. Kluwer Academic Publishers, Norwell MA, U.S.A.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957651&pid=S1409-2433201300020000800005&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[6] Glover, F.; Meli&aacute;n-Batista, B. (2003) &#8220;B&uacute;squeda tab&uacute;&#8221;, <span style="font-style: italic;">Inteligencia Artificial</span>, <span  style="font-style: italic;">Revista Iberoamericana de Inteligencia Artificial</span> 7(19): 29&#8211;48.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957652&pid=S1409-2433201300020000800006&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[7] Lara Vel&aacute;zquez, P.; L&oacute;pez Bracho, R.; Ram&iacute;rez Rodr&iacute;guez, J.; Y&aacute;&ntilde;ez, J. (2011) &#8220;A model for timetabling problems with period spread constraints&#8221;, <span style="font-style: italic;">JORS </span>62(1): 217&#8211;222.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957653&pid=S1409-2433201300020000800007&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[8] P&eacute;rez de la Cruz, C.; Ram&iacute;rez Rodr&iacute;guez, J. (2011) &#8220;Un algoritmo gen&eacute;tico para un problema de horarios con restricciones especiales&#8221;, <span style="font-style: italic;">Rev. Mat. Teor. Aplic.</span> 18(2): 215&#8211;229.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957654&pid=S1409-2433201300020000800008&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[9] Ram&iacute;rez Rodr&iacute;guez, J. (2001) <span style="font-style: italic;">Extensiones del Problema de Coloraci&oacute;n de Grafos</span>. Tesis Doctoral, Universidad Complutense de Madrid, Madrid, Espa&ntilde;a.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957655&pid=S1409-2433201300020000800009&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[10] Schaerf, A. (1996) &#8220;Tabu search techniques for large high-school timetabling problems&#8221;,<span  style="font-style: italic;"> IEEE Transactions on Systems, Man, and Cybernetics</span>: 363&#8211;368.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957656&pid=S1409-2433201300020000800010&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --></span></font><br  style="font-family: verdana;"> <br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">[11] Ya&ntilde;ez, J.; Ram&iacute;rez, J. (2003) &#8220;The robust coloring problem&#8221;, <span  style="font-style: italic;">European Journal of Operational Research</span> 148: 546&#8211;558.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1957657&pid=S1409-2433201300020000800011&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><br>     ]]></body>
<body><![CDATA[<br> </span></font>     <div style="text-align: justify;"><font size="2"><span  style="font-family: verdana;"><a name="correspondencia"></a><a  href="#Correspondencia2">*</a>Correspondencia a:</span></font><br style="font-family: verdana;"> <font size="2"> </font><font size="2"><span style="font-family: verdana;">Mario Aboytes&#8211;Ojeda. </span></font><font size="2"><span  style="font-family: verdana;">Valle de Guadiana 110 Colonia Valle del Campestre, 37150 Le&oacute;n Gto., M&eacute;xico.</span></font><font  size="2"><span style="font-family: verdana;"> (Posgrado en Ingenier&iacute;a de Sistemas, Facultad de Ingenier&iacute;a, Universidad Nacional</span></font><font  size="2"><span style="font-family: verdana;"> Aut&oacute;noma de M&eacute;xico), M&eacute;xico D.F., M&eacute;xico. E-Mail: aboalfa80@yahoo.com</span></font><br  style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Ana Lilia Laureano&#8211;Cruces. </span></font><font size="2"><span  style="font-family: verdana;">Departamento de Sistemas, Universidad Aut&oacute;noma Metropolitana, Unidad Azcapotzalco, Avenida San Pablo 180 Colonia Reynosa, 02200 M&eacute;xico D.F., M&eacute;xico; y</span></font><br style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;">Laboratoire d&#8217;Informatique d&#8217;Avignon, Universit&acute;e d&#8217;Avignon et des Pays de Vaucluse,</span></font><font  size="2"><span style="font-family: verdana;"> France. E-Mail: clc@azc.uam.mx</span></font><br style="font-family: verdana;"> <font size="2"><span style="font-family: verdana;">Javier Ram&iacute;rez&#8211;Rodr&iacute;guez.</span></font><font size="2"><span  style="font-family: verdana;">Universidad Aut&acute;onoma Metroplitana y Laboratoire d&#8217;Informatique d&#8217;Avignon, Universit&eacute; d&#8217;Avignon et des Pays de Vaucluse. Misma direcci&oacute;n que/Same address as: A.L. Laureano. E-Mail: jararo@azc.uam.mx    <br> </span></font><font size="2"><span style="font-family: verdana;"><a  name="1"></a><a href="#4">*</a>Valle de Guadiana 110 Colonia Valle del Campestre, 37150 Le&oacute;n Gto., M&eacute;xico.</span></font><br  style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;">(Posgrado en Ingenier&iacute;a de Sistemas, Facultad de Ingenier&iacute;a, Universidad Nacional</span></font><br  style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;">Aut&oacute;noma de M&eacute;xico), M&eacute;xico D.F., M&eacute;xico. E-Mail: aboalfa80@yahoo.com</span></font><br  style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;"><a name="2"></a><a href="#5">&#8224;</a>Departamento de Sistemas, Universidad Aut&oacute;noma Metropolitana, Unidad Azcapotzalco, Avenida San Pablo 180 Colonia Reynosa, 02200 M&eacute;xico D.F., M&eacute;xico; y</span></font><br style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;">Laboratoire d&#8217;Informatique d&#8217;Avignon, Universit&acute;e d&#8217;Avignon et des Pays de Vaucluse,</span></font><br  style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;">France. E-Mail: clc@azc.uam.mx</span></font><br  style="font-family: verdana;"> <font size="2"> <span style="font-family: verdana;"><a name="3"></a><a href="#6">&#8225;</a>Universidad Aut&oacute;noma Metroplitana y Laboratoire d&#8217;Informatique d&#8217;Avignon, Universit&nbsp; &acute;e d&#8217;Avignon et des Pays de Vaucluse. Misma direcci&oacute;n que/Same address as: A.L. Laureano. E-Mail: jararo@azc.uam.mx </span></font>    <br> <font size="2"><span style="font-family: verdana;"></span></font><font  size="2"><span style="font-family: verdana;"></span></font><font  size="2"><span style="font-family: verdana;"></span></font> </div> <hr style="width: 100%; height: 2px;">     <div style="text-align: center;"><font style="font-weight: bold;"  size="2"><span style="font-family: verdana;">Received: 12/Mar/2012; Revised: 15/May/2013; Accepted: 30/May/2013</span></font><br  style="font-family: verdana;"> </div> </div> </div>      ]]></body><back>
<ref-list>
<ref id="B1">
<label>1</label><nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Alvarez Valdéz]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<name>
<surname><![CDATA[Crespo]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
<name>
<surname><![CDATA[Tamarit]]></surname>
<given-names><![CDATA[J.M.]]></given-names>
</name>
</person-group>
<article-title xml:lang="en"><![CDATA[&#8220;A tabu search algorithm to schedule university examinations&#8221;]]></article-title>
<source><![CDATA[Qüestioó]]></source>
<year>1997</year>
<volume>21</volume>
<numero>1 & 2</numero>
<issue>1 & 2</issue>
<page-range>201-215</page-range></nlm-citation>
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</person-group>
<article-title xml:lang="en"><![CDATA[&#8220;Some combinatorial models for course scheduling&#8221;]]></article-title>
<source><![CDATA[PATAT&#8217;95]]></source>
<year>1995</year>
<page-range>296-308</page-range></nlm-citation>
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<source><![CDATA[An introduction to timetabling&#8221;]]></source>
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