@inproceedings{CLP-1990-GelfondL90,
	author        = "Michael Gelfond and Vladimir Lifschitz",
	booktitle     = "{Proceedings of the Seventh International Conference on Logic Programming}",
	isbn          = "0-262-73090-1",
	pages         = "579--597",
	publisher     = "{MIT Press}",
	title         = "{Logic Programs with Classical Negation}",
	year          = 1990,
}