Jesús Manuel Almendros-Jiménez Antonio Corral Solving Constraints on Sets of Spatial Objects. 158-173 2005 PADL http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3350&spage=158 conf/padl/2005 db/conf/padl/padl2005.html#Almendros-JimenezC05