1. Deparment of Mathematics and Statistics, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh, Saudi Arabia
2. Department of Mathematics, Aligarh Muslim University, Aligarh, India
3. Department of Mathematics, King Saud University, Riyadh, Saudi Arabia
4. Department of Mathematics and Statistics, College of Sciences, Taibah University, Yanbu, K.S.A