1. Department of Earth Resources Engineering, Kyushu University, Fukuoka 819-0395, Japan
2. Department of Mining Engineering, Polytechnic College, Vientiane 0100, Laos
3. Department of Mining Engineering, Faculty of Engineering, National University of Laos, Vientiane 0100, Laos
4. Lane Xang Minerals Limited, Vientiane 4486, Laos