Pfiffner, S.M., T.C. Onstott, T. Ruskeeniemi, M. Talikka, C. Bakermans, D. McGown, E. Chan, et al. 2008. “Challenges for Coring Deep Permafrost on Earth and Mars”. Astrobiology 8: 623-38. doi:10.1089/ast.2007.0159. Reference Link
Davidson, M.M., B.J. Silver, T.C. Onstott, D.P. Moser, T.M. Gihring, L.M. Pratt, E.A. Boice, et al. 2011. “Capture of Planktonic Microbial Diversity in Fractures by Long-Term Monitoring of Flowing Boreholes, Evander Basin, South Africa”. Geomicrobiology Journal 28: 275-300. doi:10.1080/01490451.2010.499928. Reference Link