1. Small denominators and problems of stability of motion in classical and celestial mechanics;Arnol′d, V. I.;Uspehi Mat. Nauk,1963
2. F. M. Arscott, Periodic differential equations, Pergamon, 1964
3. A note on isoenergetic stability;Churchill, Richard;Internat. J. Non-Linear Mech.,1977
4. Stability transitions for periodic orbits in Hamiltonian systems;Churchill, R. C.;Arch. Rational Mech. Anal.,1980
5. Hyperbolic structures in Hamiltonian systems;Churchill, R. C.;Rocky Mountain J. Math.,1977