@article{EJDE_2011__2011__a4,
     author = {Bendjeddou, Ahmed and Cheurfa, Rachid},
     title = {Cubic and quartic planar differential systems with exact algebraic limit cycles},
     journal = {Electronic Journal of Differential Equations},
     publisher = {mathdoc},
     volume = {2011},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2011__2011__a4/}
}