@article{SM_2008_199_2_a4,
     author = {A. S. Romanyuk},
     title = {Best approximations and widths of classes of periodic functions of several variables},
     journal = {Sbornik. Mathematics},
     pages = {253--275},
     publisher = {mathdoc},
     volume = {199},
     number = {2},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2008_199_2_a4/}
}