Homomorphisms of contexts and isomorphisms of concept lattices František Machala, Marek Pomp (1996) Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica
Homomorphisms of direct powers of algebras Andrzej Ehrenfeucht, Siemion Fajtlowicz, Jan Mycielski (1979) Fundamenta Mathematicae