1. Department of Mathematical Sciences, Federal Urdu University of Arts, Science & Technology, Gulshan-e-Iqbal, Karachi, Pakistan
2. Department of Mathematics, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh 221005, India
3. Mathematics Discipline, Khulna University, Khulna 9208, Bangladesh
4. Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia JB, 81310 Skudai, Johor, Malaysia