Comparison of alternative improved perturbative methods for nonlinear   oscillations
  We discuss and compare two alternative perturbation approaches for the calculation of the period of nonlinear systems based on the Lindstedt--Poincar\'{e} technique. As illustrative examples we choose one--dimensional anharmonic oscillators and the Van der Pol equation. Our results show that each approach is better for just one type of model considered here. 
Paolo Amore, Francisco Fernandez, Alfredo Raya