1. “President Bush Announces New Vision for Space Exploration Program.” NASA press release; January 14, 2004.
2. Roger D. Launius, Historical Analogs for the Stimulation of Space Commerce. NASA document No. SP-2014-4554, Washington, D. C. 2014.
3. “Commercial Orbital Transportation Services,” NASA document, Washington, D. C. February 2014. p. 3.
4. Valin Thorn, “Commercial Crew & Cargo Program Overview.” Johnson Space Center, January 11, 2007.
5. Augustine Pane, “Seeking a Human Spaceflight Program Worthy of a Great Nation,” NASA Headquarters. October 23, 2009.