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@article{DAN_1972_202_1_a2, author = {V. I. Burenkov}, title = {On the approximation of functions in $C^r(\Omega)$ where $\Omega$ is an arbitrary open set}, journal = {Doklady Akademii Nauk}, pages = {16--18}, publisher = {mathdoc}, volume = {202}, number = {1}, year = {1972}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1972_202_1_a2/} }
V. I. Burenkov. On the approximation of functions in $C^r(\Omega)$ where $\Omega$ is an arbitrary open set. Doklady Akademii Nauk, Tome 202 (1972) no. 1, pp. 16-18. http://geodesic.mathdoc.fr/item/DAN_1972_202_1_a2/