Martin, William McChesney. Letter to James E. Webb, Bureau of the Budget, Box 11, Folder 4, William McChesney Martin, Jr., Papers. https://fraser.stlouisfed.org/scribd/?item_id=456764&filepath=/files/docs/historical/martin/11_04_19470203.pdf&start_page=1, accessed on September 19, 2017.
Regarding per diem rates.
- Board of Governors of the Federal Reserve System, Federal Reserve Board
- Meltzer's History of the Federal Reserve - Primary Sources