@ARTICLE(	VG89a,
	AUTHOR = "Van Gelder, Allen",
	TITLE = "Negation as Failure Using Tight Derivations for
		General Logic Programs",
	JOURNAL = "Journal of Logic Programming",
	VOLUME = "6", NUMBER = "1",
	YEAR = "1989",
	NOTE = "Preliminary versions appeared in
		{\it Third IEEE Symp.~on Logic Programming} (1986), and
		{\it Foundations of Deductive Databases and Logic Programming},
		J.~Minker, ed., Morgan Kaufmann, 1988.",
	PAGES = "109--133"	)