@article{MZM_1991_50_4_a2,
     author = {A. S. Belov},
     title = {Partial sums of a trigonometric series with convex coefficients},
     journal = {Matemati\v{c}eskie zametki},
     pages = {21--27},
     year = {1991},
     volume = {50},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1991_50_4_a2/}
}