United States. Department of the Treasury. "Lead and Zinc, May 11, 1961," in United States. Department of the Treasury. "Volume 125," Press Releases of the United States Department of the Treasury (May 2, 1961 - May 31, 1961) : 306-312. https://fraser.stlouisfed.org/title/6111/item/586968/toc/538461 , accessed on June 24, 2024.