Xu, D., T. Feng, J. Yang, and Z. Qin. “Experimental Study on Prevention and Control of Coal-Bed Methane (CBM) Through Mining of the Protective Seam of Multiple Coal Seams”. Journal of Mines, Metals and Fuels, vol. 65, no. 10, Oct. 2017, pp. 521-3, doi:10.18311/jmmf/2017/26961.