1. Department of Chemistry, Higher Teacher Training College, University of Yaounde I, Yaounde, Cameroon
2. Department of Chemistry, Higher Teacher Training College, University of Bamenda, Bambili, Cameroon
3. Organic and Bioorganic Chemistry, Faculty of Chemistry, Bielefeld University, Bielefeld, Germany
4. H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
5. Department of Organic Chemistry, Faculty of Science, University of Yaounde I, Yaounde, Cameroon