Alexey Ershov Ilia Ivanov Serge Preis Eugene Rukoleev Dmitry Ushakov LGS: Geometric Constraint Solver. 423-430 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2890&spage=423 2003 conf/ershov/2003 Ershov Memorial Conference db/conf/ershov/ershov2003.html#ErshovIPRU03