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@article{DE_1976_12_2_a11, author = {L. A. Cherkas}, title = {Conditions for a center for a certain {Li\'enard} equation}, journal = {Differencialʹnye uravneni\^a}, pages = {292--298}, publisher = {mathdoc}, volume = {12}, number = {2}, year = {1976}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1976_12_2_a11/} }
L. A. Cherkas. Conditions for a center for a certain Li\'enard equation. Differencialʹnye uravneniâ, Tome 12 (1976) no. 2, pp. 292-298. http://geodesic.mathdoc.fr/item/DE_1976_12_2_a11/