@Article{ mag03b, author = { Magnani, Valentino }, title = { Differentiability from representation formula and Sobolev-Poincarè inequality }, journal = { Studia Math. }, year = { 2005 }, volume = { 168 }, number = { 3 }, pages = { 251-272 }, URL = { http://cvgmt.sns.it/paper/1302/ }, note = { cvgmt preprint} }