1. Inverse entailment and progol
2. Knowledge Representation, Reasoning and Declarative Problem Solving
3. Gelfond M. and Lifschitz V. 1988. The stable model semantics for logic programming. In Proc. of the 5th International Conference and Symposium, Vol. 2, August 15–19, 1988. MIT Press, Seattle, Washington, 1070–1080.
4. Kowalski R. A. and Bowen K. A. , Eds. 1988. Logic Programming, Proceedings of the 5th International Conference and Symposium, Vol. 2, August 15–19, 1988. MIT Press, Seattle, Washington.