United States. Bureau of the Census. "Cyclical Indicators," in United States. Bureau of the Census. "May 1971," Business Conditions Digest (May 1971) : 12-13. https://fraser.stlouisfed.org/title/43/item/7554/toc/129365 , accessed on April 26, 2024.
United States. Bureau of the Census. "Cyclical Indicators," in United States. Bureau of the Census. "May 1971," Business Conditions Digest (May 1971) : 12-13. https://fraser.stlouisfed.org/title/43/item/7554/toc/129365 , accessed on April 26, 2024.