First Author:   Grazia D. Santangelo University of Catania grsanta@unict.it   Via Vitt. Emanuele, 8 Catania, 95131, Italy       http://www.fscpo.unict.it/docenti/prof.ssa_Santangelo.htm Second Author: Grazia D. Santangelo University of Catania catania_2005@unict.it         http://www.fscpo.unict.it/Catania_workshop2005/