@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/}
}