1. Department of Mathematics, Karunya Institute of Technology and Sciences, Coimbatore 641 114, Tamilnadu, India
2. Department of Mathematics, PSG College of Technology, Coimbatore 641 004, Tamilnadu, India
3. Department of Mathematics, Bannari Amman Institute of Technology and Sciences, Erode 638 401, Tamilnadu, India
4. Department of Mathematics and Statistics, Manipal University Jaipur, Jaipur, Rajasthan, India
5. Jigme Namgyel Engineering College, Royal University of Bhutan, Dewathang, Thimphu, Bhutan