@article{DAN_1982_265_4_a0,
     author = {D. L. Berman},
     title = {Solution of an extremal problem in operator theory},
     journal = {Doklady Akademii Nauk},
     pages = {777--781},
     year = {1982},
     volume = {265},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1982_265_4_a0/}
}