1. Babovich, Y., Erdem, E., Lifschitz, V.: Fages’ theorem and answer set programming. In: Proc. of NMR 2000 (2000)
2. Cheeseman, P., Kanefsky, B., Taylor, W.M.: Where the Really Hard Problems Are. In: Proceedings of the Twelfth International Joint Conference on Artificial Intelligence, IJCAI 1991, Sydney, Australia, pp. 331–337 (1991)
3. Clark, K.L.: Negation as failure. In: Gallaire, H., Minker, J. (eds.) Logics and Databases, pp. 293–322. Plenum Press, New York (1978)
4. Lecture Notes in Computer Science;T. Eiter,1997
5. Fages, F.: Consistency of clark’s completion and existence of stable of stable models. Journal of Methods of Logic in Computer Science 1, 51–60 (1994)