%0 Journal Article %A Liao, Fang-Fang %T Periodic orbits with small angular momentum for singular radially symmetric systems %J Electronic Journal of Differential Equations %D 2014 %V 2014 %I mathdoc %U http://geodesic.mathdoc.fr/item/EJDE_2014__2014__a53/ %G en %F EJDE_2014__2014__a53