@inproceedings{ICLP-1991-Turi,
	author        = "Daniele Turi",
	booktitle     = "{Proceedings of the Eighth International Conference on Logic Programming}",
	isbn          = "0-262-56058-5",
	pages         = "397--411",
	publisher     = "{MIT Press}",
	title         = "{Extending S-Models to Logic Programs with Negation}",
	year          = 1991,
}