1. School of Electrical & Computer Engineering, National Technical University of Athens and Computer Technology Institute & Press "Diophantus", Patras, Greece
2. Dept. of Cultural Technology and Communication, University of Aegean and Computer Technology Institute & Press, "Diophantus", Patras, Greece
3. Dept. of Informatics, University of Piraeus
4. Dept. of Informatics & Telecommunications, University of Athens and Computer Technology Institute & Press "Diophantus", Patras, Greece
5. Dept. of Informatics, Technological Educational Institute of Athens and Computer Technology Institute & Press "Diophantus", Patras, Greece