@article{TIMM_2013_19_4_a4,
     author = {S. N. Vasil'ev},
     title = {Widths of some functional classes in the space $L_2$ on a period},
     journal = {Trudy Instituta matematiki i mehaniki},
     pages = {42--47},
     publisher = {mathdoc},
     volume = {19},
     number = {4},
     year = {2013},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMM_2013_19_4_a4/}
}