United States. Department of the Treasury. "Excess Profits Tax Regulations, February 10, 1941," in United States. Department of the Treasury. "Volume 33," Press Releases of the United States Department of the Treasury (December 26, 1940 - March 13, 1941) : 257-262. https://fraser.stlouisfed.org/title/6111/item/586875/toc/560612 , accessed on June 25, 2024.