The number of medium amplitude limit cycles of some generalized   Li\'enard systems
  We will consider two special families of polynomial perturbations of the linear center. For the resulting perturbed systems, which are generalized Li\'enard systems, we provide the exact upper bound for the number of limit cycles that bifurcate from the periodic orbits of the linear center. 
Salom\'on Rebollo-Perdomo
math.DS math.CA