%0 Journal Article %A M. Jotz %A K.-H. Neeb %T Closedness of the Tangent Spaces to the Orbits of Proper Actions %J Journal of Lie Theory %D 2008 %P 517-521 %V 18 %N 3 %U http://geodesic.mathdoc.fr/item/JOLT_2008_18_3_a1/ %F JOLT_2008_18_3_a1