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@article{MZM_1970_7_1_a4, author = {Yu. N. Subbotin}, title = {Diameter of class $W^rL$ in $L(0,2\pi)$ and spline function approximation}, journal = {Matemati\v{c}eskie zametki}, pages = {43--52}, publisher = {mathdoc}, volume = {7}, number = {1}, year = {1970}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1970_7_1_a4/} }
Yu. N. Subbotin. Diameter of class $W^rL$ in $L(0,2\pi)$ and spline function approximation. Matematičeskie zametki, Tome 7 (1970) no. 1, pp. 43-52. http://geodesic.mathdoc.fr/item/MZM_1970_7_1_a4/