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. "December 1968," Federal Reserve Bulletin (December 1968) : 165-165. https://fraser.stlouisfed.org/title/62/item/21408/toc/323925 , accessed on April 23, 2024.