United States. Department of the Treasury. "Bill Tender, June 10, 1968, Release Number f-1269," 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) : 10-11. https://fraser.stlouisfed.org/title/6111/item/587005/toc/541073 , accessed on June 24, 2024.