1. Laboratory Civil Engineering and Mechanics, National Advanced School of Engineering, The University of Yaoundé 1, Yaounde, Cameroon
2. Department of Civil Engineering, National Advanced School of Public Works, Yaounde, Cameroon
3. Laboratory of Materials, Mechanics and Civil Engineering, National Advanced School of Engineering, The University of Maroua, Maroua, Cameroon
4. Department of Civil Engineering, Advanced Teachers Training College of the Technical Education, The University of Douala, Douala, Cameroon