@inproceedings{SIGMOD-1979-Vassiliou,
	author        = "Yannis Vassiliou",
	booktitle     = "{Proceedings of the Ninth ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD79/P162.PDF",
	doi           = "10.1145/582095.582123",
	isbn          = "0-89791-001-X",
	pages         = "162--169",
	publisher     = "{ACM}",
	title         = "{Null Values in Data Base Management: A Denotational Semantics Approach}",
	year          = 1979,
}