1. Department of Mathematics, The Open University of Sri Lanka, Colombo, Nugegoda, Sri Lanka
2. Postgraduate Institute of Science, University of Peradeniya, Kandy, Peradeniya, Sri Lanka
3. Department of Mathematics, University of Peradeniya, Kandy, Peradeniya, Sri Lanka
4. Department of Mathematics, Department of Mechanical, Materials & Aerospace Engineering, University of Central Florida, Orlando, FL, USA