1. Department of Mathematics and Computer Science, University of Perugia, Via Vanvitelli, 1 – 06123 Perugia, Italy. E-mails: osvaldo.gervasi@unipg.it, sergio.tasso@unipg.it
2. Department of Computer, Control, and Management Engineering, Sapienza University of Rome, Via Ariosto, 20, Rome, Italy. E-mail: valentina.franzoni@dmi.unipg.it
3. Voc. Listricciano, 217, 06055 Papiano (PG), Italy. E-mail: matteoriganelli@gmail.com