[1] ANDRÉKA H., BURMEISTER P., NÉMETI I.:
Quasivarieties of Partial Algebras (Toward a unified model theory for Partial Algebras). Preprint Technische Hochschule Darmstadt, 1980,
MR 0608002
[2] GRÄTZER G.:
Universal Algebra. Second Edition, Springer Verlag, 1979.
MR 0538623
[5] NÉMETI I.: Operators on Classes of Algebras and the Axiom of Choice. Mathematical Institute of Hung. Acad. Sci., Preprint, June 1980.
[6] PIGOZZI D.:
On some operations on classes of algebras. Algebra Universalis 2 (1972), 346-353.
MR 0316354 |
Zbl 0272.08006