1. Bidoit, N. and Froidevaux, C., ?General logicl databases and programs default logic semantics and stratification?,J. Information and Computation, in print (1988).
2. Baral, C. and Subrahmanian, V. S., ?Stable and extension class theory for logic programs and default logics?, technical report CS-TR-2402, Dept of Computer Science, University of Maryland (February 1990). Presented at the Third International Workshop on Non-Monotonic Reasoning, South Lake Tahoe, May 1990.J. Automated Reasoning 8, 345?366 (1992).
3. Van Gelder, A., ?The alternating fixpoint of logic programs with negation?, inProceedings of the Symposium on Principles of Database Systems (1989) pp. 1?10.
4. Gelfond, M. and Lifschitz, V., ?The stable model semantics for logic programming?,Proc. 5th International Conference and Symposium on Logic Programming (eds. R. A. Kowalski and K. A. Bowen), pp. 1070?1080, Seattle, Washington, August 15?19 (1988).
5. Gelfond, M. and Lifschitz, V.,Logic Programs with Classical Negation. Proc. 7th International Conference on Logic Programming, MIT Press, pp. 579?597, 1991.