@inproceedings{KR-1991-Geffner,
	author        = "Hector Geffner",
	booktitle     = "{Proceedings of the Second International Conference on Principles of Knowledge Representation and Reasoning}",
	isbn          = "1-55860-165-1",
	pages         = "218--229",
	publisher     = "{Morgan Kaufmann}",
	title         = "{Beyond Negation as Failure}",
	year          = 1991,
}