Gihring, T. M., Moser, D. P., Lin, L. H., Davidson, M., Onstott, T. C., Morgan, L., Milleson, M., Kieft, T. L., Trimarco, E., Balkwill, D. L., Dollhopf, M. E. (2006). The distribution of microbial taxa in the subsurface water of the Kalahari Shield, South Africa, Geomicrobiol. J., 23, 415-430