Chikhachev, S. A. Kategorische Universale von Halbgruppen. (Russian) Zbl 0305.20032 Sib. Mat. Zh. 16, 149-157 (1975). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page MSC: 20M05 Free semigroups, generators and relations, word problems 20A10 Metamathematical considerations in group theory PDFBibTeX XMLCite \textit{S. A. Chikhachev}, Sib. Mat. Zh. 16, 149--157 (1975; Zbl 0305.20032)