@inproceedings{PODS-1988-UllmanV,
	author        = "Jeffrey D. Ullman and Moshe Y. Vardi",
	booktitle     = "{Proceedings of the Seventh Symposium on Principles of Database Systems}",
	cdrom         = "['journals/anthology/cd1-3:PODS88/P074.PDF', 'journals/anthology/dvd1:text/1-3/PODS88/P074.PDF']",
	doi           = "10.1145/308386.308417",
	isbn          = "0-89791-263-2",
	pages         = "74--81",
	publisher     = "{ACM}",
	title         = "{The Complexity of Ordering Subgoals}",
	year          = 1988,
}