Williams, Dr. David R. "Viking Mission to Mars" updated April 5, 2002 <http://nssdc.gsfc.nasa.gov/planetary/viking.html> (4-24-02)

Dumoulin, Jim "Project Mercury" updated August 25, 2000 <http://www.ksc.nasa.gov/History/mercury/mercury.html>(4-25-02) 

Launius, Roger D. NASA Chief Historian "The Apollo Program" updated April 22, 2002 <http://www.hq.nasa.gov/office/pao/History/apollo.html> (4-25-02)

Hamilton, Calvin J. "The First Lunar Landing" published 1989   <http://www.solarviews.com/history/EP-73/index.html>(4-24-02)

Revised: December 23, 2004 .

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