@article{MP_1961_2_6_a19,
     author = {I. P. Natanson},
     title = {{\CYRK}{\cyrr}{\cyri}{\cyrv}{\cyrery}{\cyre} {{\CYRP}{\cyre}{\cyra}{\cyrn}{\cyro}}},
     journal = {Matematicheskoe Prosveshchenie},
     pages = {227--235},
     year = {1961},
     volume = {Ser. 2, 6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MP_1961_2_6_a19/}
}