1. Department of Forestry and Wood Engineering, University of Douala, Advances Teachers Training College for Technical Education, Douala, Cameroon
2. Department of Inorganic Chemistry, University of Yaoundé I, Faculty of Science, Yaounde, Cameroon
3. Department of Chemistry, University of Douala, Faculty of Science, Douala, Cameroon
4. Department of Physics, Faculty of Science, University of Douala, Douala, Cameroon
5. Département de Chimie-Physique, Université Marien Ngouabi, Brazzaville Congo, Faculté des Sciences et Techniques, Brazzaville, Congo
6. Department of Chemistry, University of Yaoundé I, High Teacher Training College, Yaoundé, Cameroon