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@article{MZM_1991_50_6_a6, author = {N. A. Il'yasov}, title = {An~inverse approximation theorem in various metrics}, journal = {Matemati\v{c}eskie zametki}, pages = {57--65}, publisher = {mathdoc}, volume = {50}, number = {6}, year = {1991}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1991_50_6_a6/} }
N. A. Il'yasov. An~inverse approximation theorem in various metrics. Matematičeskie zametki, Tome 50 (1991) no. 6, pp. 57-65. http://geodesic.mathdoc.fr/item/MZM_1991_50_6_a6/