@Misc{ ciaespfus06, author = { Cianchi, Andrea and Esposito, Luca and Fusco, Nicola and Trombetti, Cristina }, title = { A quntitative Polya-Szego principle }, journal = { }, year = { 2006 }, pages = { }, URL = { http://cvgmt.sns.it/paper/1502/ }, note = { cvgmt preprint} }