@article{IVM_1978_8_a6,
     author = {V. \`E. Gheit},
     title = {Best mean approximation of a~cosine series with convex coefficients},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {50--55},
     year = {1978},
     number = {8},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1978_8_a6/}
}