United States. Department of the Treasury. "Bill Tender, January 29, 1968, Release Number f-1148," in United States. Department of the Treasury. "Volume 160," Press Releases of the United States Department of the Treasury (December 1, 1967 - February 29, 1968) : 494-531. https://fraser.stlouisfed.org/title/6111/item/587003/toc/540953 , accessed on June 28, 2024.