1. Global bifurcation of periodic orbits;Alexander;Amer. J. Math.,1978
2. An index for the global continuation of relatively isolated sets of periodic orbits;Alligood,1983
3. Mathematical Methods of Classical Mechanics;Arnold,1978
4. A bifurcation invariant: Degenerate orbits treated as clusters of simple orbits;Chow,1983
5. Global Hopf bifurcation from a multiple eigenvalue;Chow;Nonlinear Anal.,1978