@article{700609,
title = {On the geometric characterization of differentiability},
booktitle = {General topology and its relations to modern analysis and algebra IV},
series = {GDML\_Books},
publisher = {Society of Czechoslovak Mathematicians and Physicist},
address = {Praha},
year = {1977},
pages = {113-115},
mrnumber = {MR0426019},
zbl = {0372.46041},
url = {http://dml.mathdoc.fr/item/700609}
}
Durdil, J. On the geometric characterization of differentiability, dans General topology and its relations to modern analysis and algebra IV, GDML_Books, (1977), pp. 113-115. http://gdmltest.u-ga.fr/item/700609/