Modular elements in congruence lattices of G -sets. Vernikov, Boris M. (2000) Beiträge zur Algebra und Geometrie
Mono-unary algebras in the work of Czechoslovak mathematicians Miroslav Novotný (1990) Archivum Mathematicum
Monounary algebras with two direct limits Emília Halušková (2000) Mathematica Bohemica In this paper we describe all algebras A with one unary operation such that by a direct limit construction exactly two nonisomorphic algebras can be obtained from A .