United States. Department of the Treasury. "Bill Tender, September 18, 1967, Release Number f-1030," in United States. Department of the Treasury. "Volume 159," Press Releases of the United States Department of the Treasury (September 1, 1967 - November 29, 1967) : 154-155. https://fraser.stlouisfed.org/title/6111/item/587002/toc/540647 , accessed on May 5, 2024.