@inproceedings{LICS-1991-Statman,
	author        = "Richard Statman",
	booktitle     = "{Proceedings of the Sixth Annual Symposium on Logic in Computer Science}",
	doi           = "10.1109/LICS.1991.151643",
	isbn          = "0-8186-2230-X",
	pages         = "186--190",
	publisher     = "{IEEE Computer Society}",
	title         = "{Freyd’s Hierarchy of Combinator Monoids}",
	year          = 1991,
}