Voir la notice de l'article provenant de la source Math-Net.Ru
@article{IVM_1991_1_a1, author = {E. V. Voskresenskii}, title = {Periodic solutions of perturbed differential equations}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {11--14}, publisher = {mathdoc}, number = {1}, year = {1991}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1991_1_a1/} }
E. V. Voskresenskii. Periodic solutions of perturbed differential equations. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1991), pp. 11-14. http://geodesic.mathdoc.fr/item/IVM_1991_1_a1/