1. P. Aczel, “Non-well-founded Sets,” CSLI Lecture Notes 14, Stanford University, 1988.
2. H. Ait-Kaci, A. Podelski, and G. Smolka, “A feature-based constraint system for logic programming with entailment,” Theoretical Comp. Science 122, 1994, pp. 263–283.
3. F. Baader and K.U. Schulz, “Unification in the union of disjoint equational theories: Combining decision procedures,” in: Proc. CADE-11, LNAI 607, 1992, pp. 50–65.
4. F. Baader and K.U. Schulz, “Combination techniques and decision problems for disunification,” in: Proc. RTA-9S, LNCS 690, 1993.
5. F. Baader and K.U. Schulz, “Combination of Constraint Solving Techniques: An Algebraic Point of View,” Research Report CIS-Rep-94-75, University Munich, 1994; short version in: Proc. RTA'95, Springer LNCS 914, 1995.