@article{SM_1998_189_4_a3,
     author = {G. V. Radzievskii},
     title = {Direct and converse theorems in problems of approximation by vectors of finite degree},
     journal = {Sbornik. Mathematics},
     pages = {561--601},
     publisher = {mathdoc},
     volume = {189},
     number = {4},
     year = {1998},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1998_189_4_a3/}
}