@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/