1. On the vibrations of a particle in the plane;Yang;Int. J. Non-linear Mech.,1967
2. Natural forcing functions in nonlinear systems;Harvey;J. appl. Mech.,1958
3. Natural forcing functions in nonlinear systems;Harvey;Trans. ASME,1958
4. Steady state vibrations in systems having arbitrary restoring and arbitrary damping forces;Klotter,1953
5. Nonlinear Vibrations;Stoker,1950