United States. Department of the Treasury. "Bill Tender, July 22, 1968, Release Number f-1308," in United States. Department of the Treasury. "Volume 162," Press Releases of the United States Department of the Treasury (June 5, 1968 - September 30, 1968) : 293-294. https://fraser.stlouisfed.org/title/6111/item/587005/toc/541112 , accessed on June 24, 2024.