%0 Journal Article %A Minhós, Feliz %T Periodic solutions for a third order differential equation under conditions on the potential. %J Portugaliae mathematica %D 1998 %P 475-484 %V 55 %N 4 %I mathdoc %U http://geodesic.mathdoc.fr/item/PORMA_1998__55_4_48260/ %G en %F PORMA_1998__55_4_48260