@article{SM_1987_56_2_a12,
     author = {V. N. Rusak},
     title = {Sharp order estimates for best rational approximations in classes of functions representable as convolutions},
     journal = {Sbornik. Mathematics},
     pages = {491--513},
     publisher = {mathdoc},
     volume = {56},
     number = {2},
     year = {1987},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1987_56_2_a12/}
}