1. Bennett, F.: Quasigroup Identities and Mendelsohn Designs. Canadian Journal of Mathematics 41, 341–368 (1989)
2. Eiter, T., Faber, W., Koch, C., Leone, N., Pfeifer, G.: Dlv - a system for declarative problem solving. In: Proc. of the 8th Int. Workshop on Non-Monotonic Reasoning, NMR 2000 (2000)
3. Gelfond, M., Lifschitz, V.: The stable model semantics for logic programming. In: Proc. Fifth Int. Conf. and Symp. of Logic Programming, Seattle, WA, pp. 1070–1080 (1988)
4. Hähnle, R.: Tableaux and related methods. In: Robinson, A., Voronkov, A. (eds.) Handbook of Automated Reasoning, The MIT Press, Cambridge (2002)
5. Lecture Notes in Computer Science;R. Hasegawa,2000