Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Industrial Production - Indexes and Gross Value," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "May 1991," Federal Reserve Bulletin (May 1991) : 137-138. https://fraser.stlouisfed.org/title/62/item/20828/toc/127935 , accessed on April 24, 2024.