1. Department of Mathematics, School of Applied Sciences, University of Science and Technology, Meghalaya 793101, India
2. House No. 12, Panjabari Namghar Path, Guwahati 781037, India
3. Department of Mathematics, Arya Vidyapeeth College, Guwahati 781016, Assam, India
4. Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati 781035, Assam, India