United States. Department of the Treasury. "Annual Report of the Secretary of the Treasury on the State of the Finances for the Fiscal Year Ended June 30, 1972 : Statistical Appendix," Annual Report of the Secretary of the Treasury on the State of the Finances (Fiscal Year Ended June 30, 1972). https://fraser.stlouisfed.org/title/194/item/5609, accessed on March 27, 2025.