@article{CRMATH_2003__336_4_345_0,
     author = {Chen, Guoting and Wang, Duo and Yang, Jiazhong},
     title = {Unique normal forms for {Hopf-zero} vector fields},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {345--348},
     publisher = {Elsevier},
     volume = {336},
     number = {4},
     year = {2003},
     doi = {10.1016/S1631-073X(03)00043-8},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/S1631-073X(03)00043-8/}
}