@article{00753682, title = {Existence of periodic solutions for nonlinear Li\'enard systems.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {18}, year = {1995}, pages = {265-272}, doi = {10.1155/S0161171295000329}, zbl = {0821.34018}, language = {en}, url = {http://dml.mathdoc.fr/item/00753682} }
Kim, Wan Se. Existence of periodic solutions for nonlinear Liénard systems.. International Journal of Mathematics and Mathematical Sciences, Tome 18 (1995) pp. 265-272. doi : 10.1155/S0161171295000329. http://gdmltest.u-ga.fr/item/00753682/