United States. Bureau of the Census. "Other Key Indicators," in United States. Bureau of the Census. "May 1971," Business Conditions Digest (May 1971) : 14-14. https://fraser.stlouisfed.org/title/43/item/7554/toc/129366 , accessed on April 19, 2024.
United States. Bureau of the Census. "Other Key Indicators," in United States. Bureau of the Census. "May 1971," Business Conditions Digest (May 1971) : 14-14. https://fraser.stlouisfed.org/title/43/item/7554/toc/129366 , accessed on April 19, 2024.