1. Departments of Mathematics and Computer Science, The City University of New York, Queens College and Initiative for the Theoretical Sciences, CUNY Graduate Center, New York, USA
2. Department of Computer Science and Engineering, U.K. Department of Computer Science, Tandon School of Engineering, University of York, York, UK
3. Dipartimento di Informatica, Università degli Studi di Salerno, Fisciano, Italy
4. Dipartimento di Matematica, Università Politecnico Di Milano, Milan, Italy