1. Department of Mathematics, Graphic Era (Deemed to be University), Dehradun 248002, Uttrakhand, India
2. Mahila Maha Vidhyalaya, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India
3. Department of Mathematics, Institute of Science, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India