United States. Department of the Treasury. "Mint to stop orders for 1969 proof coin sets, November 6, 1968," in United States. Department of the Treasury. "Volume 163," Press Releases of the United States Department of the Treasury (October 1, 1968 - January 20, 1969) : 224-225. https://fraser.stlouisfed.org/title/6111/item/587006/toc/541207 , accessed on June 23, 2024.