1. Department of Chemistry, Faculty of Science, University of Douala, P. O. Box 24157, Douala, Cameroon
2. Department of Physics, Faculty of Science, University of Douala, P. O. Box 24157, Douala, Cameroon
3. Department of Forestry and Wood Engineering, Advances Teachers Training College for Technical Education, University of Douala, P. O. Box 24157, Douala, Cameroon