1. Mathematics Department, College of Science, University of Ha’il, Ha’il 2440, Saudi Arabia
2. Department of Mathematics, Faculty of Science, Mansoura University, Mansoura 35516, Egypt
3. Department of Mathematics and Statistics, College of Science, King Faisal University, P. O. Box 400, Al-Ahsa 31982, Saudi Arabia
4. Département de Mathématiques, Faculté des Sciences, Université de Lomé, 01 BP 1515 Lomé, Togo
5. Section of Mathematics, International Telematic University Uninettuno, Corso Vittorio Emanuele II, 39, 00186 Roma, Italy