APA (7th ed.) Citation

National Geographic Society (U.S.), Τέσσερα Πι, & National Geographic Society. (2012). 2012. Τέσσερα Πι.

Chicago Style (17th ed.) Citation

National Geographic Society (U.S.), Τέσσερα Πι, and National Geographic Society. 2012. Αθήνα: Τέσσερα Πι, 2012.

MLA (8th ed.) Citation

National Geographic Society (U.S.), et al. 2012. Τέσσερα Πι, 2012.