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2. Chow, S. T., and Sethna, P. R., Steady-State Damped Vibrations and Stability of a Class of Nonlinear Discrete Systems. WADC Tech. Report No. 59–543 (1960).
3. “Nonstationary Process in Nonlinear Oscillatory Systems” (Nestatsionarnye Protesessy v Nelineinykh Koleoatel'nykh Sistemakh);Mitropol'skiy,1955
4. Steady-state undamped vibrations of a class of nonlinear discrete systems;Sethna;J. appl. Mech. (Trans. ASME, Ser. E),1960
5. Sethna, P. R., Transients in certain autonomous multiple-degree-of-freedom nonlinear vibrating systems. ASME Paper No. 61.06.176. Submitted to J. appl. Mech.