%0 Journal Article %A R. Fleissner %A R. J. O'Malley %T Conditions implying the summability of approximate derivatives %J Colloquium Mathematicum %D 1979 %P 257-263 %V 41 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/cm-41-2-257-263/ %R 10.4064/cm-41-2-257-263 %G en %F 10_4064_cm_41_2_257_263