Siddiqi, A. A. (2000). Challenge to Apollo: The Soviet Union and the space race, 1945-1974. National Aeronautics and Space Administration, NASA History Div., Office of Policy and Plans.

Siddiqi, Asif A. Challenge to Apollo: The Soviet Union and the Space Race, 1945-1974. Washington, D.C.: National Aeronautics and Space Administration, NASA History Div., Office of Policy and Plans, 2000.

Siddiqi, Asif A. Challenge to Apollo: The Soviet Union and the Space Race, 1945-1974. National Aeronautics and Space Administration, NASA History Div., Office of Policy and Plans, 2000.