United States. Bureau of the Census. "Foreign Trade," in United States. Bureau of the Census. "April 1971," Business Conditions Digest (April 1971) : 73-73. https://fraser.stlouisfed.org/title/43/item/7553/toc/368685 , accessed on April 25, 2024.
United States. Bureau of the Census. "Foreign Trade," in United States. Bureau of the Census. "April 1971," Business Conditions Digest (April 1971) : 73-73. https://fraser.stlouisfed.org/title/43/item/7553/toc/368685 , accessed on April 25, 2024.