United States. Department of the Treasury. "Revised subscriptions figures for May 15 exchange, May 21, 1969," in United States. Department of the Treasury. "Volume 165," Press Releases of the United States Department of the Treasury (May 6, 1969 - August 29, 1969) : 139-140. https://fraser.stlouisfed.org/title/6111/item/587008/toc/541435 , accessed on June 22, 2024.