1. Anonymous, 2005. Exploration systems architecture study, final report. NASA-TM-2005-214062.
2. Augustine, N., 2010. Letter to representative Frank R. Wolf. March 23.
3. Potential importance of hydrogen as a future solution to environmental and transportation problems;Balat;Int. J. Hydrog. Energy,2008
4. Propellant depots for earth orbit and lunar exploration;Chandler,2007
5. Crawley, E.F., Mindell, D.A., 2010. U.S. human spaceflight: The FY11 budget and the flexible path: a space policy white paper.