@inproceedings{PPDP-2002-Chen,
	author        = "Gang Chen",
	booktitle     = "{Proceedings of the Fourth International Conference on Principles and Practice of Declarative Programming}",
	doi           = "10.1145/571157.571176",
	pages         = "181--188",
	publisher     = "{ACM}",
	title         = "{Full integration of subtyping and if-expression}",
	year          = 2002,
}