Onstott, T.C., K. Tobin, H. Dong, M.F. DeFlaun, J.K. Fredrickson, T. Bailey, F. Brockman, et al. 1997. “The Deep Gold Mines of South Africa: Windows into the Subsurface Biosphere”. In Proceedings of SPIE - The International Society for Optical Engineering, 3111:344-57. doi:10.1117/12.278789.