%0 Journal Article %A Franz Lehner %T Free operators with operator coefficients %J Colloquium Mathematicum %D 1997 %P 321-328 %V 74 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/cm-74-2-321-328/ %R 10.4064/cm-74-2-321-328 %G en %F 10_4064_cm_74_2_321_328