@inproceedings{VLDB-1991-Elmasri,
	author        = "Ramez Elmasri",
	booktitle     = "{Proceedings of the 17th International Conference on Very Large Data Bases}",
	ee            = "http://www.vldb.org/conf/1991/P067.PDF",
	isbn          = "1-55860-150-3",
	pages         = "67",
	publisher     = "{Morgan Kaufmann}",
	title         = "{Conecptual Modeling Using and Extended E-R Model}",
	year          = 1991,
}