United States. Department of the Treasury. "Customs Circular Letter No. 1924, December 14, 1938," in United States. Department of the Treasury. "Volume 25," Press Releases of the United States Department of the Treasury (October 18, 1938 - January 12, 1939) : 357-361. https://fraser.stlouisfed.org/title/6111/item/586867/toc/567467 , accessed on April 25, 2024.