1. J. Aczél,Proof of a theorem on distributive type hyperidentities, Algebra Universalis1 (1971), 1–6
2. V. D. Belousov,Systems of quasigroups with generalized identities, Uspekhi Mat. Nauk20 (1965), 75–146. English Translation: Russian Math. Surveys 20, 75–143
3. G. M. Bergman,Hyperidentities of groups and semigroups, to appear.
4. Mathematische Reihe;G. Grätzer,1978
5. G. Grötzer,Universal algebra, Second edition, Springer-Verlag, New York, Heidelberg, Berlin, 1979.