@article{1077466127, author = {Lewis, D. C.}, title = {Periodic solutions of differential equations containing a parameter}, journal = {Duke Math. J.}, volume = {22}, number = {1}, year = {1955}, pages = { 39-56}, language = {en}, url = {http://dml.mathdoc.fr/item/1077466127} }
Lewis, D. C. Periodic solutions of differential equations containing a parameter. Duke Math. J., Tome 22 (1955) no. 1, pp. 39-56. http://gdmltest.u-ga.fr/item/1077466127/