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@article{MZM_1987_41_1_a4, author = {V. A. Yudin}, title = {Jackson's theorems in $L_2$}, journal = {Matemati\v{c}eskie zametki}, pages = {43--47}, publisher = {mathdoc}, volume = {41}, number = {1}, year = {1987}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1987_41_1_a4/} }
V. A. Yudin. Jackson's theorems in $L_2$. Matematičeskie zametki, Tome 41 (1987) no. 1, pp. 43-47. http://geodesic.mathdoc.fr/item/MZM_1987_41_1_a4/