@inproceedings{CAAP-1989-Gogolla,
	author        = "Martin Gogolla",
	booktitle     = "{Proceedings of the Third International Joint Conference on Theory and Practice of Software Development, Volume 1: Colloquium on Trees in Algebra and Programming}",
	doi           = "10.1007/3-540-50939-9_137",
	isbn          = "3-540-50939-9",
	pages         = "259--274",
	publisher     = "{Springer}",
	title         = "{Algebraization and Integrity Constraints for an Extended Entity-Relationship Approach}",
	year          = 1989,
}