1. Department of Mathematics and Applied Mathematics, Virginia Commonwealth University, Richmond, V. A. 23284, USA
2. Department of Mathematics, College of Sciences, Jouf University, Saudi Arabia; naalswilem@ju.edu.sa
3. Department of Liberal Arts and Sciences, Virginia Commonwealth University in Qatar, P. O. Box 8095, Doha, Qatar; raghanam@vcu.edu
4. Department of Mathematics, University of Toledo, Toledo, O. H. 43606, USA; gerard.thompson@utoledo.edu
5. Department of Statistical Sciences and Operations Research, Virginia Commonwealth University, Richmond, V. A. 23284, USA; elboone@vcu.edu