@inproceedings{STOC-1969-Shepard,
	author        = "C. D. Shepard",
	booktitle     = "{Proceedings of the First Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/800169.805430",
	pages         = "155--163",
	publisher     = "{ACM}",
	title         = "{Languages in General Algebras}",
	year          = 1969,
}