1. Government Arts College, Coimbatore, India
2. Sri Ramakrishna College of Arts and Science, Coimbatore, India
3. Department of Mathematics, Faculty of Science, Maejo University, Chiang Mai 50290, Thailand
4. Faculty of Science and Technology, Rajamangala University of Technology Suvarnabhumi, Thailand
5. Department of Mathematics, Faculty of Science, Phuket Rajabhat University (PKRU), Thailand