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@article{DAN_1974_214_5_a13, author = {A. A. Markov}, title = {On the languages {\it {{\CYRYA}}}$_4$, {\it {{\CYRYA}}}$_5,\dots$}, journal = {Doklady Akademii Nauk}, pages = {1031--1034}, publisher = {mathdoc}, volume = {214}, number = {5}, year = {1974}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1974_214_5_a13/} }
A. A. Markov. On the languages {\it Я}$_4$, {\it Я}$_5,\dots$. Doklady Akademii Nauk, Tome 214 (1974) no. 5, pp. 1031-1034. http://geodesic.mathdoc.fr/item/DAN_1974_214_5_a13/