Some considerations concerning the presentations of universal algebras

The aim of this work is to present some proposals of a general definition of a presentation for universal algebras and some basic conclusions originating from this definition. Next, we formulate Tietze's theorem for varieties of universal algebras in a form which is a generalization of the method used in [4] for groups.The author is greatful to the referee for his helpful suggestions which influenced the version of this paper.Presented by G. Grätzer.