Gobechiya, M. I. The semigroup of varieties of biautomata is free. (Russian. English summary) Zbl 0615.20050 Tr. Tbilis. Mat. Inst. Razmadze 77, 24-35 (1985). It is proved that the semigroup of the variety of linear biautomata over a field is free (it is known that the semigroup of linear automata is not free). Reviewer: Ja.Henno Cited in 1 Document MSC: 20M35 Semigroups in automata theory, linguistics, etc. 08B20 Free algebras 20M05 Free semigroups, generators and relations, word problems 20M07 Varieties and pseudovarieties of semigroups Keywords:semigroups of varieties; variety of linear biautomata; linear automata PDFBibTeX XMLCite \textit{M. I. Gobechiya}, Proc. A. Razmadze Math. Inst. 77, 24--35 (1985; Zbl 0615.20050)