United States. Bureau of the Census. "Other Key Indicators," in United States. Bureau of the Census. "April 1972," Business Conditions Digest (April 1972) : 14-14. https://fraser.stlouisfed.org/title/43/item/7565/toc/54904 , accessed on May 4, 2024.
United States. Bureau of the Census. "Other Key Indicators," in United States. Bureau of the Census. "April 1972," Business Conditions Digest (April 1972) : 14-14. https://fraser.stlouisfed.org/title/43/item/7565/toc/54904 , accessed on May 4, 2024.