1. ASTM (American Society for Testing and Materials), 1977. Standard specification for classification of coals by rank, D 388-77. Annual Book of ASTM Standards. Part 26. Gaseous Fuels: Coal and Coke. Atmospheric Analysis. Philadelphia, PA, pp. 214– 218.
2. Determination of desorbable gas concentration of coal (direct method);Bertard;Int. J. Rock Mech. Min. Sci.,1970
3. Camp, B.S., Kidd, J.T., Lottman, L.K., Osborne, T.E., Saulsberry, Smith, J.L., Steidl, P.F., Stubbs, P.B., 1992. Geologic manual for the evaluation and development of coalbed methane. Gas Research Inst. Topical Rep. GRI-91/0110, 66 pp.
4. Chase, R.W., 1979. A comparison of methods used for determining the natural gas content of coalbeds from exploratory cores. US Dept. of Energy, METC/CR-79/18, 25 pp.
5. Diamond, W.P., 1979. Evaluation of the methane gas content of coalbeds: part of a complete coal exploration program for health and safety and resource evaluation. Proc. of the 2nd Int. Coal Exp. Symp. Miller Freeman Publications, San Francisco, CA, pp. 211–227.