@article{IM2_1978_12_2_a4,
     author = {E. P. Dolzhenko and E. A. Sevast'yanov},
     title = {On the dependence of properties of functions on their degree of approximation by polynomials},
     journal = {Izvestiya. Mathematics },
     pages = {255--288},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {1978},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1978_12_2_a4/}
}