@article{DAN_1969_187_4_a2,
     author = {Arif S. Dzhafarov},
     title = {Certain direct and inverse theorems in the theory of best approximations of functions by algebraic polynomials},
     journal = {Doklady Akademii Nauk},
     pages = {719--722},
     publisher = {mathdoc},
     volume = {187},
     number = {4},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_187_4_a2/}
}