1. Elementary Stability and Bifurcation Theory;Ioos,1980
2. Nonlinear Oscillations, Dynamical systems, and Bifurcations of Vector Fields;Guckenheimer,1983
3. MEthods of Bifurcation Theory;Chow,1982
4. Multiple-Parameter Stability Theory and Its Applications;Huseyin,1986
5. Hopf bifurcation at multiple eigenvalues;Keilhofer;Arch. Rational Mech. Anal.,1979