1. Hellenic Pasteur Institute, Athens 11521, Greece
2. Department of Electrical and Computer Engineering, University of Thessaly, Volos 38221, Greece
3. Department of Informatics and Telecommunications, National and Kapodistrian University of Athens, Athens 15784, Greece
4. Central European Institute of Technology, Masaryk University, Kamenice 735/5, 62500 Brno, Czech Republic
5. Department of Computer Science and Biomedical Informatics, University of Thessaly, Greece