Lollar, B.S., G. Lacrampe-Couloume, G.F. Slater, J. Ward, D.P. Moser, T.M. Gihring, L.-H. Lin, and T.C. Onstott. 2006. “Unravelling Abiogenic and Biogenic Sources of Methane in the Earth S Deep Subsurface”. Chemical Geology 226: 328-39. doi:10.1016/j.chemgeo.2005.09.027.