%0 Journal Article %A Volokitin, Evgenii P. %T Centering conditions for planar septic systems %J Electronic Journal of Differential Equations %D 2003 %V 2003 %I mathdoc %U http://geodesic.mathdoc.fr/item/EJDE_2003__2003__a113/ %G en %F EJDE_2003__2003__a113