Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "Net Ton-Miles, Revenue and Nonrevenue," in Board of Governors of the Federal Reserve System (U.S.), 1935- and Federal Reserve Board, 1914-1935. "May 1921," Federal Reserve Bulletin (May 1921) : 98-98. https://fraser.stlouisfed.org/title/62/item/20523/toc/260763 , accessed on May 9, 2024.