@article{ZVMMF_1977_17_1_a0,
     author = {A. I. Grebennikov and V. A. Morozov},
     title = {Optimal approximation of operators},
     journal = {\v{Z}urnal vy\v{c}islitelʹnoj matematiki i matemati\v{c}eskoj fiziki},
     pages = {3--14},
     publisher = {mathdoc},
     volume = {17},
     number = {1},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZVMMF_1977_17_1_a0/}
}