1. Department of Mathematics and Computer Science, Avram Iancu University of Cluj-Napoca, Cluj-Napoca, Romania
2. Romanian Institute of Science and Technology, Cluj-Napoca, Romania
3. Department of Applied Cybernetics, Saint-Petersburg State University, Saint-Petersburg, Russia
4. Department of Mathematical Information Technology, University of Jyväskylä, 40014 Jyväskylä, Finland
5. Department of Electronic Engineering, City University of Hong Kong, Hong Kong SAR, China