@article{EMJ_2013_4_3_a9,
     author = {G. A. Yusupov},
     title = {Best polynomial approximations and widths of certain classes of functions in the space~$L_2$},
     journal = {Eurasian mathematical journal},
     pages = {120--126},
     publisher = {mathdoc},
     volume = {4},
     number = {3},
     year = {2013},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EMJ_2013_4_3_a9/}
}