@article{DAN_1970_192_5_a0,
     author = {B. M. Budak and E. M. Berkovich},
     title = {The approximation of extremal problems},
     journal = {Doklady Akademii Nauk},
     pages = {959--962},
     publisher = {mathdoc},
     volume = {192},
     number = {5},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_192_5_a0/}
}