1. Stoker, J.J.: Nonlinear Vibrations in Mechanical and Electrical Systems. Interscience, New York (1950)
2. Nayfeh, A.H., Mook, D.T.: Nonlinear Oscillations. Wiley, New York (1979)
3. Hagedorn, P.: Nonlinear Oscillations. Clarendon, Oxford (1988). (translated by Wolfram Stadler)
4. Krylov, N.M., Bogoliubov, N.N.: Introduction to Non-linear Mechanics. Princeton University Press, New Jersey (1949). (translated by Solomon Lefschetz)
5. Bogoliubov, N.N., Mitropolsky, Y.A.: Asymptotic Methods in the Theory of Nonlinear Oscillations. Gordon and Breach, New York (1961)