Bryan, C. D. B. (1987). The National Geographic Society: 100 years of adventure and discovery. H.N. Abrams.
Cita Chicago (17th ed.)Bryan, C. D. B. The National Geographic Society: 100 Years of Adventure and Discovery. New York: H.N. Abrams, 1987.
Cita MLA (9th ed.)Bryan, C. D. B. The National Geographic Society: 100 Years of Adventure and Discovery. H.N. Abrams, 1987.
Atenció: Aquestes cites poden no estar 100% correctes.