United States. Department of the Treasury. "Lead and Zinc, July 11, 1963, Release Number d-903," in United States. Department of the Treasury. "Volume 137," Press Releases of the United States Department of the Treasury (June 4, 1963 - August 4, 1963) : 253-257. https://fraser.stlouisfed.org/title/6111/item/586980/toc/539197 , accessed on June 23, 2024.