4Takens F, Singularities of vector fields [J]. Publ Math I H E S, 1974,43(1):47-100.
5Ushiki S, Normal forms for singularities of vector fields [J]. Japan J Appl Math, 1984(1) : 1-37.
6Chen Gting,Wang Duo,Yang Jiazhong. Unique orbital normal form for vector fields of hopf-zero singularity [J]. Journal of Dynsmies and Differential Equations, 2005,17 (1): 3-18.
7Baider A, Sanders J. Further reduction of the Takens-Bogdanov normal form [J]. Journal of Differential Equation, 1992,99(3) : 205-244.
8Wang Duo, Li Jing, Huang Minhai. Unique normal form of Bogdanov-Takens singularities [J]. Journal of Differential Equation, 2000,163 (6) : 223-238.
