Ulrich Endriss Paolo Mancarella Fariba Sadri Giacomo Terreni Francesca Toni The CIFF Proof Procedure for Abductive Logic Programming with Constraints. 31-43 http://dx.doi.org/10.1007/978-3-540-30227-8_6 2004 conf/jelia/2004 JELIA db/conf/jelia/jelia2004.html#EndrissMSTT04