@inproceedings{OOPSLA-1987-BorningDFKW,
	author        = "Alan Borning and Robert Duisberg and Bjørn N. Freeman-Benson and Axel Kramer and Michael Woolf",
	booktitle     = "{Proceedings of the Second Conference on Object-Oriented Programming, Systems, Languages and Applications}",
	doi           = "10.1145/38765.38812",
	editor        = "Norman K. Meyrowitz",
	isbn          = "0-89791-247-0",
	pages         = "48--60",
	publisher     = "{ACM}",
	title         = "{Constraint Hierarchies}",
	year          = 1987,
}