%0 Journal Article %A Salsa, Sandro %T Viscosity Solutions of Two-Phase Free Boundary Problems for Elliptic and Parabolic Operators %J Bollettino della Unione matematica italiana %D 2012 %P 263-280 %V 5 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/item/BUMI_2012_9_5_2_a5/ %G en %F BUMI_2012_9_5_2_a5