United States. Bureau of the Census. "Foreign Trade," in United States. Bureau of the Census. "April 1971," Business Conditions Digest (April 1971) : 19-19. https://fraser.stlouisfed.org/title/43/item/7553/toc/368654 , accessed on March 28, 2024.
United States. Bureau of the Census. "Foreign Trade," in United States. Bureau of the Census. "April 1971," Business Conditions Digest (April 1971) : 19-19. https://fraser.stlouisfed.org/title/43/item/7553/toc/368654 , accessed on March 28, 2024.