@article{MZM_1978_23_5_a3,
     author = {W. Dahmen},
     title = {Best approximation and de la {Vall\'ee{\textendash}Poussin} sums},
     journal = {Matemati\v{c}eskie zametki},
     pages = {671--683},
     year = {1978},
     volume = {23},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1978_23_5_a3/}
}