%0 Journal Article %A L. Rubel %T Differentiability of monotonic functions %J Colloquium Mathematicum %D 1963 %P 277-279 %V 10 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/cm-10-2-277-279/ %R 10.4064/cm-10-2-277-279 %G en %F 10_4064_cm_10_2_277_279