@inproceedings{NACLP-1990-Spencer,
	author        = "Bruce Spencer",
	booktitle     = "{Proceedings of the North American Conference on Logic Programming, 2 Volumes}",
	isbn          = "0-262-54058-4",
	pages         = "569--584",
	publisher     = "{MIT Press}",
	title         = "{Avoiding Duplicate Proofs}",
	year          = 1990,
}