1. Erzwungene schwingungen bei veränderlicher eigenfrequenz;Duffing,1918
2. Perturbation methods;Nayfeh,1973
3. Non-linear oscillations;Nayfeh,1979
4. Homotopy perturbation technique;He;Comput Methods Appl Mech Engrg,1999
5. Fractal characterization of evolving trajectories of duffing oscillator;Salau;Int J Adv Eng Technol,2012