1. N. Krylov and N. Bogoliubov, Les méthodes de la mécarique nonlinéaire, Monographie 8, Chaire de la Physics and Mathematics of Academic Science, U.K. (1934).
2. Asymptotic Methods in the Theory of Nonlinear Oscillations;Bogoliubov,1961
3. Nonlinear Oscillations;Nayfeh,1979
4. The subharmonic bifurcation solution of nonlinear Mathieu’s equation and Euler dynamically buckling problem;Chen;Acta Mech. Sinica,1988
5. Methods of Bifurcation Theory;Chow,1982