1. ----, Indonesia Energy Statistics,Ministry of Energy and Mineral Resources (2010).
2. ----, Indonesian standard on coal resorces and reserves classification (1998).
3. Hawkins,L.V. et all., Coal seam structure delineation by downhole-crosshole seismic methods, Geoexploration, 24, pp.409-419 (1987).
4. Hoek,E., Practical Rock Engineering (2007).
5. Ismail, M.N., A multichannel velocity filter with application to borehole seismology (1988).