1. Department of Computer Science, University of Verona, Strada Le Grazie 15, 34134 Verona, Italy
2. Department of Information Engineering, University of Padova, Via G. Gradenigo 6/b, 35131 Padova, Italy
3. Department of Mathematics and Computer Science, University of Udine, Via delle Scienze 206, 33100 Udine, Italy
4. Department of Industrial Engineering-Chemical Sector, University of Padova, Via F. Marzolo 9, 35131 Padova, Italy