"NASA Innovative Advanced Concepts"(PDF). AIAA SPACE 2013 Conference and Exposition (AIAA 2013-5376). September 10, 2013. Archived from the original(PDF) on 1 December 2020. Retrieved 17 November 2021.
NASA Institute for Advanced Concepts, 9th Annual & Final Report, 2006-2007, Performance Period July 12, 2006 - August 31, 2007 (page 9, Executive Summary, 4th paragraph)
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"NASA Innovative Advanced Concepts"(PDF). AIAA SPACE 2013 Conference and Exposition (AIAA 2013-5376). September 10, 2013. Archived from the original(PDF) on 1 December 2020. Retrieved 17 November 2021.