1. Department of Mathematics, Faculty of Science, Mansoura University, Mansoura 35516, Egypt
2. Department of Statistics and Operations Research, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
3. Department of Mathematics and Computer Science, Transilvania University of Brasov, 500036 Brasov, Romania
4. Academy of Romanian Scientists, 050045 Bucharest, Romania