@article{DAN_1961_140_3_a0,
     author = {D. L. Berman},
     title = {Extremal problems in the theory of polynomial operators (non-periodic case)},
     journal = {Doklady Akademii Nauk},
     pages = {519--521},
     publisher = {mathdoc},
     volume = {140},
     number = {3},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_140_3_a0/}
}