1. Wilhelm-Schickard-Institut für Informatik, Universität Tübingen, Sand 14, 72076, Tübingen, Germany
2. Computer Science Department, University of California, Irvine, Donald Bren School of Information and Computer Sciences, Irvine, 92697-3435, CA, USA
3. Department of Engineering, Roma Tre University, Via Della Vasca Navale 79, 00146, Rome, Italy
4. Department of Computer Science, University of Crete, Heraklion, Greece