1. Perturbation Methods;Nayhef,1973
2. Nonlinear Oscillations;Nayhef,1979
3. Asimptoticheskie Metodi v teorii Nelinejnih Kolebanij;Bogoliubov,1974
4. Nonlinear Oscillations, Dynamical Systems and Bifurcation of Vector Fields;Guckenheimer,1980
5. On a gradient method in nonconservative mechanics;Vujanovic;Acta Mech.,1979