1. African Higher Institute of Managerial and Technological Education, P.O. Box 1743, Bonanjo, Douala, Cameroon
2. Department of Mechanical Engineering, College of Technology, University of Buea, P.O. Box 63, Buea, Cameroon
3. Department of Basic Scientific Teaching, School of Geology and Mining Engineering, University of Ngaoundere, P.O. Box 115, Meiganga, Cameroon
4. Laboratory of Ore and Mineral Processing, Institute for Geology and Mining Research, P.O. Box 4110, Yaounde, Cameroon
5. Department of Mechanical, Petroleum and Gas Engineering, National Advanced School of Mines and Petroleum Industries, University of Maroua, P.O. Box 46, Maroua, Cameroon