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@article{IVM_1966_1_a12, author = {K. E. Malkin}, title = {Conditions for the center for a~class of differential equations}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {104--114}, publisher = {mathdoc}, number = {1}, year = {1966}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1966_1_a12/} }
K. E. Malkin. Conditions for the center for a~class of differential equations. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1966), pp. 104-114. http://geodesic.mathdoc.fr/item/IVM_1966_1_a12/