@misc{MP_2021_3_28_a20,
     title = {{\CYRP}{\cyro}{\cyrp}{\cyrr}{\cyra}{\cyrv}{\cyrk}{\cyra}},
     journal = {Matematicheskoe Prosveshchenie},
     pages = {263},
     year = {2021},
     volume = {Ser. 3, 28},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MP_2021_3_28_a20/}
}