United States. Bureau of the Budget and United States. Office of Management and Budget. "Budget Receipts by Source," in United States. Bureau of the Budget and United States. Office of Management and Budget. "Fiscal Year 1969," Budget of the United States Government (January 29, 1968) : 539-539. https://fraser.stlouisfed.org/title/54/item/19022/toc/380790 , accessed on April 18, 2024.