@article{EJDE_2007__2007__a33,
     author = {Alwash, Mohamad Ali M.},
     title = {Complex centers of polynomial differential equations},
     journal = {Electronic Journal of Differential Equations},
     publisher = {mathdoc},
     volume = {2007},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2007__2007__a33/}
}