HOW FINITE IS A THREE-ELEMENT UNARY ALGEBRA?
J. HYNDMAN, Jane G. Pitkethly · International Journal of Algebra and Computation · 2005
We show that, within the class of three-element unary algebras, there is a tight connection between a finitely based quasi-equational theory, finite rank, enough algebraic operations (from natural duality theory) and a special injectivity condition.