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@article{MZM_1993_53_4_a11, author = {O. I. Smirnov}, title = {The {Jackson} theorem in $L_2$ for {Christenson--Levy} systems}, journal = {Matemati\v{c}eskie zametki}, pages = {111--130}, publisher = {mathdoc}, volume = {53}, number = {4}, year = {1993}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1993_53_4_a11/} }
O. I. Smirnov. The Jackson theorem in $L_2$ for Christenson--Levy systems. Matematičeskie zametki, Tome 53 (1993) no. 4, pp. 111-130. http://geodesic.mathdoc.fr/item/MZM_1993_53_4_a11/