@article{DAN_1991_320_1_a6,
     author = {S. M. Nikol'skii},
     title = {Approximation of functions by trigonometric polynomials on a
},
     journal = {Doklady Akademii Nauk},
     pages = {40--44},
     publisher = {mathdoc},
     volume = {320},
     number = {1},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_320_1_a6/}
}