1. Department of Industrial Engineering and Maintenance, Polytechnic University of Mongo, Mongo, Chad
2. Department of Physics, Faculty of Exact and Applied Sciences, University of Ndjamena (Scientific Facilitator in Cecoqda), Ndjamena, Chad
3. Department of Fundamental and Transversal Sciences, National Advanced School of Public Works, Yaoundé, Cameroon
4. Department of Civil Engineering, Advanced Teacher Training College of the Technical Education, University of Douala, Douala, Cameroon