Siebert, Charles (July 2011). "Food Ark". National Geographic. 220 (1): 108–131. OCLC741814684. Archived from the original on 2011-06-19. Retrieved 2017-02-24.
Siebert, Charles (July 2011). "Food Ark". National Geographic. 220 (1): 108–131. OCLC741814684. Archived from the original on 2011-06-19. Retrieved 2017-02-24.
"Donors". CropTrust.org. Archived from the original on 11 January 2015. Retrieved 3 July 2011.
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Siebert, Charles (July 2011). "Food Ark". National Geographic. 220 (1): 108–131. OCLC741814684. Archived from the original on 2011-06-19. Retrieved 2017-02-24.