1. Department of Mathematical Sciences, Delaware State University, Dover, DE 19901-2277, USA
2. Department of Mathematics, Howard University, Washington, DC 20059, USA
3. Faculty of Electronic Engineering, Department of Telecommunications, University of Nis, Aleksandra Medvedeva 14, 18000 Nis, Serbia
4. Department of Engineering Sciences, Faculty of Technology and Engineering, East of Guilan, University of Guilan, P.C. 44891-63157, Rudsar-Vajargah, Iran
5. Department of Mathematics, Faculty of Mathematical Sciences, University of Mazandaran, Babolsar, Iran
6. Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
7. Science Program, Texas A & M University at Qatar, P.O. Box 23874, Doha, Qatar