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@article{DAN_1991_320_2_a4, author = {V. I. Prokhorenko}, title = {Theorems on the smoothness of periodic solutions of differential}, journal = {Doklady Akademii Nauk}, pages = {280--283}, publisher = {mathdoc}, volume = {320}, number = {2}, year = {1991}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1991_320_2_a4/} }
V. I. Prokhorenko. Theorems on the smoothness of periodic solutions of differential. Doklady Akademii Nauk, Tome 320 (1991) no. 2, pp. 280-283. http://geodesic.mathdoc.fr/item/DAN_1991_320_2_a4/