1. Department of Mathematics, Sacred Heart College (Autonomous), Tirupattur, 635 601 Tamilnadu, India
2. Department of Mathematics, Faculty of Science, Maejo University, Chiang Mai 50290, Thailand
3. Department of Mathematics, Faculty of Science and Technology, Phuket Rajabhat University, Phuket 83000, Thailand
4. Department of Mathematics, Faculty of Science and Technology, Rajamangala University of Technology Suvarnabhumi, Nonthaburi 11000, Thailand
5. Department of Mathematics, Aden University, Khormaksar, P.O. Box 6014, Yemen