@article{article1021422a,
title   = {Normalization of complex-valued planar vector fields which degenerate along a real curve},
author = {Cordaro, Paulo Domingos and Gong, Xianghong},
year = {2004},
doi = {10.1016/S0001-8708(03)00139-7},
journal   = {Advances in Mathematics}
}