Martin C. Cooper Simon de Givry Thomas Schiex Optimal Soft Arc Consistency. 68-73 2007 conf/ijcai/2007 IJCAI http://dli.iiit.ac.in/ijcai/IJCAI-2007/PDF/IJCAI07-009.pdf db/conf/ijcai/ijcai2007.html#CooperGS07