1. Laboratory of modeling Materials and Methods of the National Higher Polytechnic School, Douala University, Douala, Cameroon
2. Electrical engineering department, The National Higher Institute of Mao, N’DJAMENA, Tchad
3. Electrical engineering department, INSPEM, Malaysia
4. Institute of Technology, Douala University, Douala, Cameroon
5. Higher normal school of Technical Education, Douala University, Douala, Cameroon