G. Iooss and M. , Adelmeyer: Topics in Bifurcation Theory and Applications, 1992.

L. Jézéquel and C. Lamarque, Analysis of non-linear dynamical systems by the normal form theory, Journal of Sound and Vibration, vol.149, issue.3, pp.429-459, 1991.
DOI : 10.1016/0022-460X(91)90446-Q

C. Touzé, O. Thomas, and A. , Hardening/softening behaviour in non-linear oscillations of structural systems using non-linear normal modes, Journal of Sound and Vibration, vol.273, issue.1-2, pp.77-101, 2004.
DOI : 10.1016/j.jsv.2003.04.005

A. D. Brjuno, Analytical Forms of Differential Equations, Trudy Mosk, Mat. Obshest, vol.25, pp.199-299, 1971.

C. Lamarque, E. Professor, . Dgcb, and . Cnrs, Rue Maurice Audin, 69518 Vaulx-en-Velin Cedex, France, the author gave a presentation of this paper during one of the conference sessions (lamarque@entpe.fr)

O. Thomas, Assistant Professor: CNAM, LMSSC, 2 rue Conté