[1] Chien Wei-zang(ed.),Singular Perturbotion Theory and Its Applications in Mechanics,Science Press,Beijing(1981).(in Chinese).
[2] Kevorkian,J.and J.D.Cole,Perturbation Methods in Applied Mathematics,Springer-Verlag. New York(1981).
[3] Kuzmak.G.E.,Asymptotic solutions of nonlinear second order diftensity variable cofficients,PMM(USSR).23(1959).515-526. (in Russian).
[4] Luke,J.C..A perturbation method for nonlinear dispersive wave problems.Proc.Roy.Soc Ser,A292(1966).403-412.
[5] Whitham.G.B.,Linear and Nonlinear Waves.John Wiley & Sons.Inc.,New York (1974).
[6] Burton,T.D.,Non-linear oscillator limit cycle analysis using a time transformation approach.Int.J.Non-Linear Mech.,17(1982).7-19.
[7] Bogoliubov.N.N.and Y.A.Mitropolsky,Asymptotic Methods in the Theory of Nonlinear Oscillations.4th Ed.,“Nauka”Press,Moscow(1974) (in Russian).
[8] Byrd,P.F.and M.D.Friedman.Handbook of Elliptic Integrals for Engineers and Scientist 2nd Ed.,Springer-Verlag.New York(1971).