1. Department of Mathematics, University of the Punjab, Lahore 54590, Pakistan
2. Department of Mathematics, COMSATS University Islamabad, Attock Campus, Attock, Pakistan
3. Universiti Kuala Lumpur Malaysian Institute of Industrial Technology, Persiaran Sinaran Ilmu Bandar Seri Alam, 81750 Masai, Johor Bahru, Johor, Malaysia