1. Department of Mathematics, College of Science, King Khalid University , P.O. Box 9004, 61413 , Abha , Saudi Arabia
2. Department of Mathematics, Faculty of Science, South Valley University , 83523 , Qena , Egypt
3. Department of Basic Sciences, University of Engineering and Technology , Peshawar , Pakistan
4. Department of Mathematical Sciences, College of Science, Princess Nourah bint Abdulrahman University , P.O.Box 84428 , Riyadh 11671 , Saudi Arabia