United States. Department of the Treasury. "U.S. Savings Bonds Issued and Redeemed through July 1971, August 6, 1971," in United States. Department of the Treasury. "Volume 174," Press Releases of the United States Department of the Treasury (July 1, 1971 - August 31, 1971) : 340-341. https://fraser.stlouisfed.org/title/6111/item/587017/toc/542367 , accessed on June 25, 2024.