%0 Journal Article %A Zhang, Shuqin %T Positive solutions for boundary-value problems of nonlinear fractional differential equations %J Electronic Journal of Differential Equations %D 2006 %V 2006 %I mathdoc %U http://geodesic.mathdoc.fr/item/EJDE_2006__2006__a164/ %G en %F EJDE_2006__2006__a164