Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Selected Business Indexes," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "May 1971," Federal Reserve Bulletin (May 1971) : 125-125. https://fraser.stlouisfed.org/title/62/item/21437/toc/8202 , accessed on April 25, 2024.