Isabel Navarrete Antonio Morales Guido Sciavicco Consistency Checking of Basic Cardinal Constraints over Connected Regions. 495-500 2007 conf/ijcai/2007 IJCAI http://dli.iiit.ac.in/ijcai/IJCAI-2007/PDF/IJCAI07-078.pdf db/conf/ijcai/ijcai2007.html#NavarreteMS07