1. On the correctness of unfold/fold transformation of normal and extended logic programs;Aravindan;J. Logic Programming,1994
2. Non-monotonic learning;Bain,1992
3. Logic programming and knowledge representation;Baral;J. Logic Programming,1994
4. A useful four-valued logic;Belnap,1975
5. Biconsequence relations for nonmonotonic reasoning;Bochman,1996