Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Index of Production of Minerals, by Products," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "July 1928," Federal Reserve Bulletin (July 1928) : 28-28. https://fraser.stlouisfed.org/title/62/item/20679/toc/289835 , accessed on March 28, 2024.