Electronic Journal of Differential Equations, Vol.
Any equilibrium generates a manifold of equilibria under the action of the group.
We prove that, if the manifold of equilibria is normally hyperbolic, an invariant manifold persists in the neighborhood under any small perturbation which may break the symmetry. The Liapunov-Perron approach of integral equations is used. This and other articles are avilable in DVI, PDF, PS, and TeX format. Thanks to the European Mathematical Information Service, the EJDE and other journals have mirror copies through the world. Here is a partial listing of mirror sites.