@article{GDZPPN00223310X,
title = {A characterization of C1-convex sets in Sobolev spaces.},
journal = {Manuscripta mathematica},
volume = {76},
year = {1992},
pages = {247-272},
zbl = {0766.46014},
url = {http://dml.mathdoc.fr/item/GDZPPN00223310X}
}
Dal Maso, G.; Defranceschi, Anneliese. A characterization of C1-convex sets in Sobolev spaces.. Manuscripta mathematica, Tome 76 (1992) pp. 247-272. http://gdmltest.u-ga.fr/item/GDZPPN00223310X/