1. Department of International Trade, Technological Educational Institute of Western Macedonia at Kastoria, P. O. Box 30, GR-521 00, Kastoria, Greece
2. Department of Informatics and Computer Technology, Technological Educational Institute of Western Macedonia at Kastoria, P. O. Box 30, GR-521 00, Kastoria, Greece
3. Department of Mathematics, College of Sciences, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia
4. Laboratory of Computational Sciences, Department of Computer Science and Technology, Faculty of Sciences and Technology, University of Peloponnese, GR-22 100 Tripolis, Greece