@article{DAN_1979_248_5_a2,
     author = {A. P. Buslaev},
     title = {On best approximation of the differentiation operator},
     journal = {Doklady Akademii Nauk},
     pages = {1041--1044},
     publisher = {mathdoc},
     volume = {248},
     number = {5},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1979_248_5_a2/}
}