REFERENCES
- Gerard IoossDaniel D. Joseph Elementary Stability and Bifurcation Theory . New York, Heidelberg, Berlin 1980 .
- J. E. Marsden and M. McCracken The Hopf Bifurcation and its Applications , Springer-Verlag . New York , 1976 .
- B. D. Hassard. N D. Kazarinoff and Y-H. Wan Theory and Application of Hopf Bifurcation , London Mathematical Society Lecture Notes Series, No. 41 . Cambridge University Press , Cambridge , 1981 .