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@article{MZM_1979_26_2_a15, author = {B. S. Kashin}, title = {General orthonormal systems and certain problems of approximation theory}, journal = {Matemati\v{c}eskie zametki}, pages = {299--315}, publisher = {mathdoc}, volume = {26}, number = {2}, year = {1979}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1979_26_2_a15/} }
B. S. Kashin. General orthonormal systems and certain problems of approximation theory. Matematičeskie zametki, Tome 26 (1979) no. 2, pp. 299-315. http://geodesic.mathdoc.fr/item/MZM_1979_26_2_a15/