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@article{DE_1972_8_12_a12, author = {K. S. Sibirskii}, title = {The problem of an algebraic integral in the case of the center}, journal = {Differencialʹnye uravneni\^a}, pages = {2211--2214}, publisher = {mathdoc}, volume = {8}, number = {12}, year = {1972}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1972_8_12_a12/} }
K. S. Sibirskii. The problem of an algebraic integral in the case of the center. Differencialʹnye uravneniâ, Tome 8 (1972) no. 12, pp. 2211-2214. http://geodesic.mathdoc.fr/item/DE_1972_8_12_a12/