@inproceedings{ICLP-1987-ClarkG87,
	author        = "Keith L. Clark and Steve Gregory",
	booktitle     = "{Proceedings of the Fourth International Conference on Logic Programming, 2 Volumes}",
	isbn          = "0-262-12125-5",
	pages         = "927--961",
	publisher     = "{MIT Press}",
	title         = "{PARLOG and PROLOG United}",
	year          = 1987,
}