Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1966_2_3_a14, author = {V. I. Voilokov}, title = {On the question of existence of periodic solutions with an arbitrary period}, journal = {Differencialʹnye uravneni\^a}, pages = {422--424}, publisher = {mathdoc}, volume = {2}, number = {3}, year = {1966}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1966_2_3_a14/} }
V. I. Voilokov. On the question of existence of periodic solutions with an arbitrary period. Differencialʹnye uravneniâ, Tome 2 (1966) no. 3, pp. 422-424. http://geodesic.mathdoc.fr/item/DE_1966_2_3_a14/