1. Department of Mathematics, University of Malakand, Chakdara, Dir Lower, 18000, Khyber Pakhtunkhwa, Pakistan
2. Department of Mathematics, Kuwait College of Science and Technology, Safat 13133, P. O. Box 27235, Kuwait
3. Department of Mathematical Sciences, United Arab Emirates University, P. O. Box 15551, Al Ain, Abu Dhabi, UAE