Cita APA (7a ed.)

Anderson, N. D., & Allen Hynek, J. (1962). Challenge of the universe. National science teachers association.

Cita Chicago Style (17a ed.)

Anderson, Norman D., y J. Allen Hynek. Challenge of the Universe. Washington: National science teachers association, 1962.

Cita MLA (8a ed.)

Anderson, Norman D., y J. Allen Hynek. Challenge of the Universe. National science teachers association, 1962.