1. "CommercialSpaceTransportationStudy"http://www.hq.nasa.gov/webaccess/CommSpaceTrans/ViewedJuly 19,2005.
2. Greenberg,J.S.,Hertzfeld,H.R.,Ed."SpaceEconomics".Prog.inAstronauticsandAeronautics,Vol.144, AIAA,Washington,DC, 1992.
3. RobertS.Walker,Chair, "Anyone,Anytime,Anything,Anywhere".FinalReportofthePresident'sCommission on the Future of theUnited States AerospaceIndustry".November,2002.
4. Aldridge,E.C.,Fiorina,C.S.,Jackson,M.P.,Leshin,L.A., Lyles,L.L.,Spudis,P.D.,Tyson,N.d.,Walker,R.S., Zuber, M.T. "A Journey to Inspire, Innovate, and Discover". Report of the President's Commission on Implementation of United StatesSpaceExploration Policy". Washington DC, June2004.