1. Physical and Theoretical Chemistry of Laboratory, University of Yaoundé 1, Yaoundé, Cameroon
2. Laboratory of Theoretical Chemistry (LCT) and Namur Institute of Structured Matter (NISM), University of Namur, Rue de Bruxelles, 61, B-5000 Namur, Belgium
3. Department of Chemistry, High Teacher Training College, University of Yaoundé 1, Yaoundé, Cameroon