APA (7th ed.) Citation

National Geographic Society, Washington, D. C., Chamberlin, W., & Grosvenor, G. H. (1950). The round earth on flat paper. Map projections used by cartographers. [s. n.

Chicago Style (17th ed.) Citation

National Geographic Society, Washington, D. C., Wellman Chamberlin, and Gilbert Hovey Grosvenor. The Round Earth on Flat Paper. Map Projections Used by Cartographers. Washington: [s. n, 1950.

MLA (9th ed.) Citation

National Geographic Society, Washington, D. C., et al. The Round Earth on Flat Paper. Map Projections Used by Cartographers. [s. n, 1950.