@article{1178229636,
author = {Martelli, Mario and Schuur, Jerry D.},
title = {Periodic solutions of Li\'enard type second order ordinary differential equations},
journal = {Tohoku Math. J. (2)},
volume = {32},
number = {4},
year = {1980},
pages = { 201-207},
language = {en},
url = {http://dml.mathdoc.fr/item/1178229636}
}
Martelli, Mario; Schuur, Jerry D. Periodic solutions of Liénard type second order ordinary differential equations. Tohoku Math. J. (2), Tome 32 (1980) no. 4, pp. 201-207. http://gdmltest.u-ga.fr/item/1178229636/