Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Group Index Numbers - United States, Bureau of Labor Statistics," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "March 1921," Federal Reserve Bulletin (March 1921) : 70-70. https://fraser.stlouisfed.org/title/62/item/20521/toc/249259 , accessed on April 27, 2024.