1. Department of Electrical and Information Engineering, Polytechnic of Bari, 70125 Bari, Italy
2. Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University di Messina, Messina 98166, Italy
3. Department of Biomedical, Dental, Morphological and Functional Imaging Sciences, University of Messina, Messina 98125, Italy
4. Institute of Applied and Computational Mathematics, FORTH, GR-70013 Heraklion, Crete, Greece