Voir la notice de l'article provenant de la source Math-Net.Ru
@article{IVM_1958_1_a5, author = {E. I. Zheleznov}, title = {Some sufficient conditions for the existence of limit cycles}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {56--59}, publisher = {mathdoc}, number = {1}, year = {1958}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1958_1_a5/} }
E. I. Zheleznov. Some sufficient conditions for the existence of limit cycles. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1958), pp. 56-59. http://geodesic.mathdoc.fr/item/IVM_1958_1_a5/