1. Department of Mathematics, College of Science and Arts, Al-Qurayat, Jouf University, Sakaka, Saudi Arabia
2. Department of Mathematics, Faculty of Science, Mansoura University, Mansoura, Egypt
3. Department of Mathematics and Computer Science, Transilvania University of Brasov, Brasov, Romania
4. Academy of Romanian Scientists, Bucharest, Romania
5. Aerospace Engineering Department, Politecnico di Torino, Torino, Italy