1. School of Mathematics and Statistics, Taiyuan Normal University, Taiyuan 030024, Shanxi, P. R. China
2. College of Computer and Information Science, University of Arkansas at Little Rock, Little Rock, AR 72204, USA
3. College of Mathematics, Government College University Faisalabad, Faisalabad 38000, Pakistan
4. Department of Computer Science and Mathematics, Lebanese American University, Beirut 11022801, Lebanon
5. Robert H. Smith School of Business, University of Maryland, College Park, MD 20740, USA
6. Department of Mathematics, Saveetha School of Engineering, SIMATS Chennai, India
7. Department of Mathematics, Kwame Nkrumah, University of Science and Technology, Kumasi, Ghana