1. Department of Mathematics Federal University of Technology Owerri Owerri Nigeria
2. Laboratoire Lmdan, Département de Mathématiques de la Décision, Facultédes Sciences Economiques et Gestion Université Cheikh Anta Diop de Dakar Dakar Fann Senegal
3. Department of Mathematics University of Hawaii Manoa Honolulu Hawaii USA
4. Networked Systems Lab, IT Covergence Engineering, School of Electronic Engineering Kumoh National Institute of Technology Gumi Korea
5. Department of Mathematics University of Benin Benin City Nigeria