1. Department of Mathematics, Faculty of Science, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia
2. Institute for Mathematical Research, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia
3. Centre for Computational Finance & Economic Agents, University of Essex, Colchester CO4 3SQ, UK
4. Mathematical Sciences, University of KwaZulu-Natal, Westville Campus, Durban 3001, South Africa
5. Essex Business School, University of Essex, Colchester CO4 3SQ, UK