Pressel, P., & Allen, N. (2013). Meeting the challenge: The Hexagon KH-9 reconnaissance satellite. Published by American Institute of Aeronautics and Astronautics, Inc..

Pressel, Philip, and Ned Allen. Meeting the Challenge: The Hexagon KH-9 Reconnaissance Satellite. Reston, Virginia: Published by American Institute of Aeronautics and Astronautics, Inc., 2013.

Pressel, Philip, and Ned Allen. Meeting the Challenge: The Hexagon KH-9 Reconnaissance Satellite. Published by American Institute of Aeronautics and Astronautics, Inc., 2013.