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"The HEXAGON story"(PDF). National Reconnaissance Office (NRO). 1988. Archived from the original(PDF) on 16 September 2012. Retrieved 6 October 2011. This article incorporates text from this source, which is in the public domain.
Richard J. Chester (1985). "A history of the HEXAGON program". National Reconnaissance Office (NRO). Archived from the original on 15 September 2012. Retrieved 24 September 2011. This article incorporates text from this source, which is in the public domain.
"The HEXAGON story"(PDF). National Reconnaissance Office (NRO). 1988. Archived from the original(PDF) on 16 September 2012. Retrieved 6 October 2011. This article incorporates text from this source, which is in the public domain.
Richard J. Chester (1985). "A history of the HEXAGON program". National Reconnaissance Office (NRO). Archived from the original on 15 September 2012. Retrieved 24 September 2011. This article incorporates text from this source, which is in the public domain.