Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Series Included in the Index of Industrial Production," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "August 1940," Federal Reserve Bulletin (August 1940) : 19-21. https://fraser.stlouisfed.org/title/62/item/21028/toc/49908 , accessed on April 26, 2024.