Non-isomorphism of categories of algebras

TL;DR

This paper discusses the non-isomorphism of categories of algebras, addressing a mathematical problem that was lost during historical upheavals and rediscovered later.

Contribution

It provides a proof or argument demonstrating that certain categories of algebras are not isomorphic, clarifying a longstanding mathematical question.

Findings

Categories of algebras are not isomorphic.

The paper clarifies the structure of algebraic categories.

Historical context of the paper's rediscovery.

Abstract

This paper was accepted for Comment. Math. Univ. Carolinae in 1968 but then got lost during the military occupation of Prague and surrounding events. My own long-lost carbon copy of it turned up in my Columbia office. The only changes to the text are addition of a footnote and some commas.