Board of Governors of the Federal Reserve System (U.S.), 1935-. "Market Groupings, Seasonally Adjusted," in Board of Governors of the Federal Reserve System (U.S.), 1935-. "April 15, 1981," G.12.3 Industrial Production (1981-04-15) : 4-4. https://fraser.stlouisfed.org/title/55/item/59643/toc/472168 , accessed on May 7, 2024.