@inproceedings{SIGMOD-1984-KellerU,
	author        = "Arthur M. Keller and Jeffrey D. Ullman",
	booktitle     = "{Proceedings of the 14th ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD84/P143.PDF",
	doi           = "10.1145/602259.602279",
	pages         = "143--148",
	publisher     = "{ACM Press}",
	title         = "{On Complementary and Independent Mappings on Databases}",
	year          = 1984,
}