@inproceedings{SIGMOD-1990-UllmanY,
	author        = "Jeffrey D. Ullman and Mihalis Yannakakis",
	booktitle     = "{Proceedings of the 20th ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD90/P044.PDF",
	doi           = "10.1145/93597.93620",
	pages         = "44--53",
	title         = "{The Input/Output Complexity of Transitive Closure}",
	year          = 1990,
}