Marcos Calle Sebastián Lozano Kate A. Smith Terence Kwok Juan José Domínguez A DTD for an XML-Based Mathematical Modeling Language. 968-977 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2660&spage=968 2003 conf/iccS/2003-4 International Conference on Computational Science db/conf/iccS/iccS2003-4.html#CalleLSKD03