1. Associate Professor, Univ. of Cassino and Southern Lazio, via di Biasio 43, 03043 Cassino, Italy (corresponding author).
2. Associate Professor, Univ. of Napoli Federico II, via Claudio 21, 80125 Napoli, Italy.
3. Associate Professor, Univ. of Marconi, via Plinio 44, 00193 Roma, Italy.
4. Silesian Univ. of Technology, Ulica Akademicka 5, 44100 Gliwice, Poland.
5. Professor, Univ. of Cassino and Southern Lazio, via di Biasio 43, 03043 Cassino, Italy.