1. Department of Computer Science, University of Peshawar, Peshawar 25120, Pakistan
2. Centre of Excellence in IT, Institute of Management Sciences, Hayatabad, Peshawar, Pakistan
3. Department of Computer Science, Abdul Wali Khan University Mardan, Pakistan
4. Department of Mathematics, University of Peshawar, Peshawar 25120, Pakistan
5. TEI of Thessaloniki, Sindos, 57400 Thessaloniki, Greece
6. Brunel University, Uxbridge UB8 3PH, UK