Howard, Mingos, ed. (1937). The Aircraft Year Book for 1937(PDF). New York: Aeronautical Chamber of Commerce of America. pp. 231–232. Archived from the original(PDF) on 16 August 2021. Retrieved 7 March 2021.
Weingroff, Richard F. (May–June 2000). "One Mile in Five: debunking the myth". Public Roads. Vol. 63, no. 6. Federal Highway Administration. Archived from the original on 25 October 2021. Retrieved 7 March 2021.
Weingroff, Richard F. (May–June 2000). "One Mile in Five: debunking the myth". Public Roads. Vol. 63, no. 6. Federal Highway Administration. Archived from the original on 25 October 2021. Retrieved 7 March 2021.
Howard, Mingos, ed. (1937). The Aircraft Year Book for 1937(PDF). New York: Aeronautical Chamber of Commerce of America. pp. 231–232. Archived from the original(PDF) on 16 August 2021. Retrieved 7 March 2021.