@inproceedings{SIGMOD-1981-Richard,
	author        = "Philippe Richard",
	booktitle     = "{Proceedings of the 11th ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD81/P155.PDF",
	doi           = "10.1145/582318.582343",
	pages         = "155--163",
	publisher     = "{ACM Press}",
	title         = "{Evaluation of the Size of a Query Expressed in Relational Algebra}",
	year          = 1981,
}