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 15, 1975," G.12.3 Industrial Production (1975-04-15) : 8-8. https://fraser.stlouisfed.org/title/55/item/59795/toc/469968 , accessed on April 23, 2024.