Semivarieties and Schreier varieties of unary algebras

A. I. Budkin

Novosibirsk State University

Abstract: A correction is provided for one result of a paper by Shafaat [1], and it is proven that the set of Schreier varieties of algebras $\left<A;{}^+1\right>$ with two unary operations has the cardinality of the continuum.

 English version: Mathematical Notes, 1974, 15:2, 150–154

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