@inproceedings{SIGMOD-1990-RosenthalG,
	author        = "Arnon Rosenthal and César A. Galindo-Legaria",
	booktitle     = "{Proceedings of the 20th ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD90/P291.PDF",
	doi           = "10.1145/93597.98738",
	pages         = "291--299",
	title         = "{Query Graphs, Implementing Trees, and Freely-Reorderable Outerjoins}",
	year          = 1990,
}