Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1981_17_4_a17, author = {N. N. Butenina}, title = {Multiple merging of separatrices and limit cycles}, journal = {Differencialʹnye uravneni\^a}, pages = {732--734}, publisher = {mathdoc}, volume = {17}, number = {4}, year = {1981}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1981_17_4_a17/} }
N. N. Butenina. Multiple merging of separatrices and limit cycles. Differencialʹnye uravneniâ, Tome 17 (1981) no. 4, pp. 732-734. http://geodesic.mathdoc.fr/item/DE_1981_17_4_a17/