1. Perturbation Methods;Nayfeh,1973
2. Oscillations in Planar Dynamics Systems;Mickens,1996
3. Nonlinear Ordinary Differential Equations;Jordan,1987
4. Nonlinear Oscillations (translated by WolframStadler);Hagedorn,1981
5. Non-Perturbative Methods for Strongly Nonlinear Problems Dissertion;He,2006