1. Department of Applied Mathematics and Statistics, Institute of Space Technology, P. O. Box 2750, Islamabad 44000, Pakistan
2. School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM Penang, Malaysia
3. Department of Mathematics, Deanship of Applied Sciences, Umm Al-Qura University, Makkah, Saudi Arabia
4. Department of Mathematics, Huzhou University, Huzhou, Zhejiang 313000, P. R. China
5. Institute for Advanced Study Honoring Chen Jian Gong, Hangzhou Normal University Hangzhou, Zhejiang 211121, P. R. China
6. Department of Mathematics, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia