@article{DAN_1969_184_5_a6,
     author = {P. L. Ul'yanov},
     title = {Imbedding theorems and best approximations},
     journal = {Doklady Akademii Nauk},
     pages = {1044--1047},
     publisher = {mathdoc},
     volume = {184},
     number = {5},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_184_5_a6/}
}