1. Nonlinearity and Functional Analysis. Lectures on Nonlinear Problems in Mathematical Analysis;Berger,1977
2. Celestial Mechanics. Analytical and Qualitative Methods;Duboshin,1964
3. General problem of stability of motion;Lyapunov;Int. J. Control,1992
4. The Hopf Bifurcation and Its Applications;Marsden,1976
5. Periodic orbits near an equilibrium and a theorem by A. Weinstein;Moser;Commun. Pure Appl. Math.,1976