@inproceedings{POPL-1993-KozenPS,
	author        = "Dexter Kozen and Jens Palsberg and Michael I. Schwartzbach",
	booktitle     = "{Conference Record of the 20th Annual Symposium on Principles of Programming Languages}",
	doi           = "10.1145/158511.158700",
	editor        = "Mary S. Van Deusen and Bernard Lang",
	isbn          = "0-89791-560-7",
	pages         = "419--428",
	publisher     = "{ACM Press}",
	title         = "{Efficient Recursive Subtyping}",
	year          = 1993,
}