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@article{TM_1967_89_a3, author = {V. I. Burenkov}, title = {On the additivity of the classes of $W_p^{(r)}(\Omega )$}, journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova}, pages = {31--55}, publisher = {mathdoc}, volume = {89}, year = {1967}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/TM_1967_89_a3/} }
V. I. Burenkov. On the additivity of the classes of $W_p^{(r)}(\Omega )$. Trudy Matematicheskogo Instituta imeni V.A. Steklova, Investigations in the theory of differentiable functions of many variables and its applications. Part 2, Tome 89 (1967), pp. 31-55. http://geodesic.mathdoc.fr/item/TM_1967_89_a3/