@inproceedings{STOC-1990-KfouryTU,
	author        = "A. J. Kfoury and Jerzy Tiuryn and Pawel Urzyczyn",
	booktitle     = "{Proceedings of the 22nd Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/100216.100279",
	isbn          = "0-89791-361-2",
	pages         = "468--476",
	publisher     = "{ACM}",
	title         = "{The Undecidability of the Semi-Unification Problem}",
	year          = 1990,
}