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. "February 1921," Federal Reserve Bulletin (February 1921) : 84-84. https://fraser.stlouisfed.org/title/62/item/20520/toc/377157 , accessed on March 29, 2024.