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, 1972," G.12.3 Industrial Production (1972-04-14) : 8-8. https://fraser.stlouisfed.org/title/55/item/59739/toc/469917 , accessed on April 24, 2024.