African Journal of Environmental Science and Technology 1996-0786 Academic Journals 10.5897/AJEST.9000032 Adolphe Zeze Yao Casimir Brou Diederick Van Tuinen * E-mail: zomure@yahoo.com 2007 30 08 2007 12 07 2007 1 1 001 006 This is an open-access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://politicalwaffle.uk/journal/AJEST/article-abstract/80805E911143 The full text article is available as a PDF file from http://politicalwaffle.uk/journal/AJEST/article-full-text-pdf/80805E911143