1. Computer Science and Mathematics, University of L'Aquila, Center of Excellence DEWS, Via Vetoio, Coppito,Department of Information Engineering,L'Aquila,Italy,67100
2. Istituto di Analisi dei Sistemi e Informatica “A. Ruberti”, Italian National Research Council (IASI-CNR),Rome,Italy,00185
3. New Enterprise Technology University G. D'Annunzio,Pescara,Italy