1. Section of Mathematics, International Telematic University Uninettuno, Corso Vittorio Emanuele II, 39, 00186 Roma, Italy
2. Department of Mathematical Sciences, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
3. Department of Mathematics, College of Education for Pure Sciences, University of Basrah, Basrah 61001, Iraq
4. Doctoral School of Mathematical and Computational Sciences, University of Debrecen, H-4002 Debrecen, Pf. 400, Hungary
5. Department of Mathematics, Mahendra College of Engineering, Affiliated to Anna University, Chennai, Salem (Dt), Tamil Nadu, India
6. Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
7. Department of Mathematic, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia