@inproceedings{KR-1989-DoyleW,
	author        = "Jon Doyle and Michael P. Wellman",
	booktitle     = "{Proceedings of the First International Conference on Principles of Knowledge Representation and Reasoning}",
	isbn          = "1-55860-032-9",
	pages         = "94--102",
	publisher     = "{Morgan Kaufmann}",
	title         = "{Impediments to Universal Preference-Based Default Theories}",
	year          = 1989,
}