National Geographic Television, Willumsen, G., & Kiley, R. (2009). 30 years of National Geographic specials. National Geographic.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNational Geographic Television, Gail Willumsen, और Richard Kiley. 30 Years of National Geographic Specials. [Washington, D.C.]: National Geographic, 2009.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNational Geographic Television, et al. 30 Years of National Geographic Specials. National Geographic, 2009.
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