@article{SM_1997_188_9_a5,
     author = {K. Yu. Osipenko},
     title = {On the precise values of $n$-widths for classes defined by cyclic variation diminishing operators},
     journal = {Sbornik. Mathematics},
     pages = {1371--1383},
     year = {1997},
     volume = {188},
     number = {9},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1997_188_9_a5/}
}