Van Voast, Wayne A., 2002, Geochemical signature of formation waters associated with coalbed methane, The American Association of Petroleum Geologists Bulletin, v. 87, No. 4 (April 2003), pp. 667-676. 

Van Voast, W., and P. Thale, Anderson and Knobloch coal horizons and potential for methane development, Powder River Basin, Montana: Montana Bureau of Mines and Geology Geologic Map 60, (2001).