1. A note on clones with nullary operations. How clones should be;Behrisch,2011
2. Category theoretic understandings of universal algebra and its dual: monads and Lawvere theories, comonads and what?;Behrisch,2012
3. A course in universal algebra;Burris,1981
4. Universal algebra;Cohn,1965
5. Adjoint functors and triples;Eilenberg;Illinois J. Math.,1965