[1] Sikkim Manipal Univ, Sikkim Manipal Inst Technol, Dept Math, Rangpo 737136, East Sikkim, India
[2] Beluti MKM High Sch, PO Beluti, Beluti 731301, WB, India
[3] Visva Bharati, Siksha Bhavana, Dept Math, Santini Ketan 731235, W Bengal, India
[4] Univ Malaya, Dept Phys, Plasma Technol Res Ctr, Kuala Lumpur 50603, Malaysia