United States. Department of the Treasury. "Lead and Zinc, May 16, 1963, Release Number d-850," in United States. Department of the Treasury. "Volume 136," Press Releases of the United States Department of the Treasury (April 23, 1963 - May 31, 1963) : 370-372. https://fraser.stlouisfed.org/title/6111/item/586979/toc/539145 , accessed on June 23, 2024.