TY - JOUR AU - Laurence, Peter AU - Stredulinsky, Edward TI - A comparison principle for an American option on several assets: index and spread options JO - Electronic journal of differential equations PY - 2003 VL - 2003 UR - http://geodesic.mathdoc.fr/item/EJDE_2003__2003__a121/ LA - en ID - EJDE_2003__2003__a121 ER -