@article{DAN_1976_227_6_a4,
     author = {A. V. Ostrovsky},
     title = {$k$-covering mappings},
     journal = {Doklady Akademii Nauk},
     pages = {1297--1300},
     publisher = {mathdoc},
     volume = {227},
     number = {6},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1976_227_6_a4/}
}