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@article{MZM_1986_39_5_a3, author = {A. G. Babenko}, title = {The exact constant in the {Jackson} inequality in $L^2$}, journal = {Matemati\v{c}eskie zametki}, pages = {651--664}, publisher = {mathdoc}, volume = {39}, number = {5}, year = {1986}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1986_39_5_a3/} }
A. G. Babenko. The exact constant in the Jackson inequality in $L^2$. Matematičeskie zametki, Tome 39 (1986) no. 5, pp. 651-664. http://geodesic.mathdoc.fr/item/MZM_1986_39_5_a3/