United States. Department of the Treasury. "Bill Offering, December 23, 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) : 538-540. https://fraser.stlouisfed.org/title/6111/item/587006/toc/541263 , accessed on June 23, 2024.