@article{DAN_1967_175_6_a7,
     author = {R. L. Frum-Ketkov},
     title = {Mappings into a sphere of a {Banach} space},
     journal = {Doklady Akademii Nauk},
     pages = {1229--1231},
     publisher = {mathdoc},
     volume = {175},
     number = {6},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1967_175_6_a7/}
}