Integration of Functions in the Fixpoint Semantics of Rule-Based Systems. - Erik Lambrichts; Peter Nees; Jan Paredaens; Peter Peelman; Letizia Tanca (MFDBS, 1989)

Integration of Functions in Logic Database Systems. - Erik Lambrichts; Peter Nees; Jan Paredaens; Peter Peelman (Data Knowl. Eng., 1990)

Checking Functional Consistency in Deductive Databases. - Erik Lambrichts; Peter Nees; Jan Paredaens; Peter Peelman; Letizia Tanca (Inf. Process. Lett., 1990)