1. Ali, S.M., Pattanayal, P., Shubhra, 2012. Underground coal gasification techniques, problems and its solutions. International Journal of Engineering and Innovative Technology, 2(3):129–134.
2. Antonova, R.I., Bezhanishvili, A.I., Blinderman, M.S., et al., 1990. Underground Coal Gasification. Central Research Institute of Economics and Scientific-Technical Information of Coal Industry Press, Moscow (in Russian).
3. Arens, V.Z., 1986. Mining by Boreholes. Nedra, Moscow (in Russian).
4. Chen, X.X., Luo, Z.J., Zhou, S.L., 2014. Influences of soil hydraulic and mechanical parameters on land subsidence and ground fissures caused by groundwater exploitation. Journal of Hydrodynamics, Ser. B, 26(1):155–164. [doi:10.1016/S1001-6058(14)60018-4]
5. Clements, B.R., 1977. Progress report for the Texas utilities UCG program. Proceedings of the 3rd Annual Underground Coal Conversion Symposium, Lawrence Livermore Laboratory, California, USA, p.81–82.