1. Geometrical Methods in the Theory of Ordinary Differential Equations;Arnold,1982
2. Methods of Bifurcation Theory;Chow,1982
3. Normal forms of bifurcating periodic orbits;Chow,1986
4. Splitting algorithm for nilpotent normal form;Cushman,1987
5. A simple global characterization for normal forms of singular vector fields;Elphick,1986