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2. R. Churchill, M. Kummer, and D. Rod, 1983, “On averaging, reduction and symmetry in Hamiltonian systems”, J. Diff. Eqns., 49, 359–414.
3. R. Cushman, 1992, “A survey of normalization techniques applied to perturbed Keplerian systems”, Dynamics reported, (new series) 1, 54–112, (New York: Springer).
4. J-C.van der Meer, 1985, The Hamiltonian Hopf bifurcation, Lecture Notes in Mathematics, 1185, (New York: Springer).
5. R. Cushman and L. Bates, Global Aspects of Classical Integrable Systems, (to appear).