1. Department of Mathematics, University of Montpellier, Montpellier, France;
2. Resource Economics, West Virginia University, Morgantown, West Virginia, USA;
3. Institute of Basic Sciences, Technology and Innovation, Pan African University, Nairobi, Kenya;
4. Department of Economics, University FHB, Abidjan, Cote-d’Ivoire;
5. Department of Finance, Wayne State University, Detroit, Michigan, USA