Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Group Index Numbers-Belgium-Ministry of Labor," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "May 1923," Federal Reserve Bulletin (May 1923) : 69-69. https://fraser.stlouisfed.org/title/62/item/20548/toc/370070 , accessed on March 28, 2024.