1. School of Computer Science and Technology, Shandong Technology and Business University, Yantai, P.R. China
2. School of Computer Science, University of St Andrews, St Andrews, UK
3. Department of Mathematics, Khwaja Fareed University of Engineering & Information Technology, Rahim Yar Khan, Pakistan
4. Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen, Thailand
5. Department of Basic Sciences, College of Sciences and Theoretical Studies, Dammam-branch, Saudi Electronic University, Riyad, Saudi Arabia