1. Department of Physics and Earth
Sciences, University of Messina, Viale
Ferdinando Stagno D’Alcontres 31, 98166 Messina, Italy
2. Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo,
Trento, Italy
3. IPCF CNR, UOS Roma, I-00185 Roma, Italy
4. Department of Computer Science, University of Verona, Strada le Grazie 15, 37134 Verona,
Italy
5. Department of Physics, University of Perugia, Via A. Pascoli, 06123 Perugia,
Italy