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@article{DAN_1973_211_4_a3, author = {V. G. Durnev}, title = {Positive theory of a free semigroup}, journal = {Doklady Akademii Nauk}, pages = {772--774}, publisher = {mathdoc}, volume = {211}, number = {4}, year = {1973}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1973_211_4_a3/} }
V. G. Durnev. Positive theory of a free semigroup. Doklady Akademii Nauk, Tome 211 (1973) no. 4, pp. 772-774. http://geodesic.mathdoc.fr/item/DAN_1973_211_4_a3/