@article{paperid:102927,
author = {Afsharnejad, Zahra},
title = {pesistences of periodic trajectories of planar systems under two parametric perturbations},
journal = {Journal of the Korean Mathematical Society},
year = {2007},
month = {February},
issn = {0304-9914},
keywords = {periodic Trajectotys- Perturbation- Planar systems- Poincare map- Van der Pol equation},
}