United States. Department of the Treasury. "U.S. Savings Bonds Issued and Redeemed through March 31, 1970, April 7, 1970," in United States. Department of the Treasury. "Volume 168," Press Releases of the United States Department of the Treasury (February 2, 1970 - April 30, 1970) : 440-441. https://fraser.stlouisfed.org/title/6111/item/587011/toc/541732 , accessed on June 25, 2024.