@article{CRMATH_2003__336_9_709_0,
     author = {Ren, Zhihua and Yang, Jiazhong},
     title = {On the {\protect\emph{C}\protect\textsuperscript{1}} normal forms for hyperbolic vector fields},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {709--712},
     publisher = {Elsevier},
     volume = {336},
     number = {9},
     year = {2003},
     doi = {10.1016/S1631-073X(03)00173-0},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/S1631-073X(03)00173-0/}
}