1. Graduate School of International Resource Sciences Akita University Akita City Japan
2. Department of Geological Engineering Universitas Gadjah Mada Yogyakarta Indonesia
3. Faculty of Science Universiti Brunei Darussalam Bandar Seri Begawan Brunei Darussalam
4. PT Kapuas Prima Coal, TBk. Pantai Indah Kapuk North Jakarta Indonesia