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/archival/1341/item/456764, accessed on August 19, 2018.
Regarding per diem rates.
- Board of Governors of the Federal Reserve System, Federal Reserve Board
- Meltzer's History of the Federal Reserve - Primary Sources