@article{1077469038, author = {Cronin, Jane}, title = {The number of periodic solutions of non-autonomous systems}, journal = {Duke Math. J.}, volume = {27}, number = {1}, year = {1960}, pages = { 183-193}, language = {en}, url = {http://dml.mathdoc.fr/item/1077469038} }
Cronin, Jane. The number of periodic solutions of non-autonomous systems. Duke Math. J., Tome 27 (1960) no. 1, pp. 183-193. http://gdmltest.u-ga.fr/item/1077469038/