1. University of Chieti-Pescara, Viale Pindaro 42, 65127, Pescara, Italy. {emanuele.deangelis,fabio.fioravanti,cmeo}@unich.it
2. University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy. pettorossi@info.uniroma2.it
3. IASI-CNR, Via dei Taurini 19, 00185 Rome, Italy. maurizio.proietti@iasi.cnr.it