| A. Brogi, E. Lamma, P. Mello, Open Logic Theories, Proceedings of the II Workshop on Extensions of Logic Programming (WELP91), Kista, Sweden, 1991, also in H.H.Erikkson, P.Krueger and P.Schroeder-Heister (eds.), Lecture Notes in Artificial Intelligence No. 596 Springer-Verlag, Berlin. |