@article{DAN_1963_150_6_a7,
     author = {N. P. Korneichuk},
     title = {The exact value of best approximations and widths of certain classes of functions},
     journal = {Doklady Akademii Nauk},
     pages = {1218--1220},
     publisher = {mathdoc},
     volume = {150},
     number = {6},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_150_6_a7/}
}