United States. Department of the Treasury. "Preliminary Statistics of Income Tax Returns for 1936, February 21, 1938," in United States. Department of the Treasury. "Volume 22," Press Releases of the United States Department of the Treasury (December 15, 1937 - April 15, 1938) : 415-419. https://fraser.stlouisfed.org/title/6111/item/586863/toc/567158 , accessed on April 19, 2024.