First Author:   W. Adrian Risso University of Siena risso@unisi.it         Second Author: Juan Gabriel Brida School of Economics and Management - Free University of Bolzano JuanGabriel.Brida@unibz.it   Via Sernesi 1 Bolzano, 39100, Italy   +39 0471 013492(Phone) +39 0471 013009(Fax) http://www.unibz.it/