1. Aandrea, S. O. [1971] On the decision problem for formulas in which all disjunctions are binary, Proc 2nd Scandinavian Logic Symposium, North Holland, Amsterdam, pp 1–18
2. Apt, K. R, Blair, H. and Walker, A. [1988] Towards a theory of declarative knowledge. (to appear)
3. Borger, E. [1971] Reduktionstypen in Krom-und Hornformeln Dissertation Universitat Muenster, (the respective part of the above Dissertation was published in the paper cited next below)
4. [Borger, E. [1974] Beitrag zur Reduktion des Entscheidungproblems auf Klassen von Hornformeln mit kurzem Alternation, Arch. f. mathematische Logik u. Grundlagenforschung 16(1974), 67–84
5. Lassez, C. McAloon, K. and Port, G. [1987] Stratification and Knowledge Base Management in: Proc Fourth Int. Conf. Logic Programming J.-L. Lassez (editor) MIT Press, pp. 136–151