1. Clark, K.L. 1978, “Negation as Failure” In Logic and Data Bases (H. Gallaire and J. Minker, Eds.), Plenum Press, New York, N.Y., 1978, 293–322.
2. Davis, M. 1980, “The Mathematics of Non-Monotonic Reasoning”, Artificial Intelligence Journal, 13, 2 (April 1980), 73–80.
3. Hewitt, C. 1972, “Descrintion and Theoretical Analysis (Using Schemata) of PLANNER: A Language for Proving Theorems and Manipulating Models in a Robot”, AI Memo No. 251, MIT Project MAC, Cambridge, Mass., April 1980.
4. Hill, R. 1974, “LUSH Resolution and its Completeness” DCL Memo No. 78, University of Edinburg School of Artificial Intelligence, August 1974.
5. Kowalski, R.A. and Kuehner, D. 1971, “Linear Resolution with Selection Function” Artificial Intelligence Vol. 2, 1971, 227–260.