@inproceedings{POPL-1991-AmadioC,
	author        = "Roberto M. Amadio and Luca Cardelli",
	booktitle     = "{Conference Record of the 18th Annual Symposium on Principles of Programming Languages}",
	doi           = "10.1145/99583.99600",
	editor        = "David S. Wise",
	isbn          = "0-89791-419-8",
	pages         = "104--118",
	publisher     = "{ACM Press}",
	title         = "{Subtyping Recursive Types}",
	year          = 1991,
}