1. ADJAN S Defining relations and algorithmic problems for groups and semlgroups Proc Stektov lnst Math 85 1966 {Enlish version published by American Mathematical Society 1967} ADJAN S Defining relations and algorithmic problems for groups and semlgroups Proc Stektov lnst Math 85 1966 {Enlish version published by American Mathematical Society 1967}
2. BERSTEL J Congruences plus que parfaites et languages algdbnque Semmair d'Informattque Thdonque lnstltut de Programmatmn 1976-77 pp 123-147 BERSTEL J Congruences plus que parfaites et languages algdbnque Semmair d'Informattque Thdonque lnstltut de Programmatmn 1976-77 pp 123-147
3. BOOK R JANTZEN M AND WRAIHALL C Monadlc Thue systems To appear m Theor Comput SCI BOOK R JANTZEN M AND WRAIHALL C Monadlc Thue systems To appear m Theor Comput SCI