@article{EJDE_2007__2007__a233,
     author = {Alwash,  Mohamad Ali M.},
     title = {Complex centers of polynomial differential equations},
     journal = {Electronic journal of differential equations},
     year = {2007},
     volume = {2007},
     zbl = {1138.34311},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2007__2007__a233/}
}