Board of Governors of the Federal Reserve System (U.S.), 1935-. "Summary Groupings, Seasonally Adjusted," in Board of Governors of the Federal Reserve System (U.S.), 1935-. "April 14, 1977," G.12.3 Industrial Production (1977-04-14) : 8-8. https://fraser.stlouisfed.org/title/55/item/59519/toc/470182 , accessed on May 1, 2024.