Burgess, George W. Letter to Richard N. Johnson, Box 13, Folder 4, William McChesney Martin, Jr., Papers. https://fraser.stlouisfed.org/scribd/?item_id=456895&filepath=/files/docs/historical/martin/13_04_19460225.pdf&start_page=1, accessed on September 20, 2017.
Regarding estimates for American-flag and foreign-flag airlines
- Board of Governors of the Federal Reserve System, Federal Reserve Board
- Meltzer's History of the Federal Reserve - Primary Sources