Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1972_8_9_a18, author = {M. V. Dolov}, title = {Limit cycles in the case of the center}, journal = {Differencialʹnye uravneni\^a}, pages = {1691--1692}, publisher = {mathdoc}, volume = {8}, number = {9}, year = {1972}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1972_8_9_a18/} }
M. V. Dolov. Limit cycles in the case of the center. Differencialʹnye uravneniâ, Tome 8 (1972) no. 9, pp. 1691-1692. http://geodesic.mathdoc.fr/item/DE_1972_8_9_a18/