United States. Bureau of the Census. "Composite Indexes," in United States. Bureau of the Census. "April 1971," Business Conditions Digest (April 1971) : 40-41. https://fraser.stlouisfed.org/title/43/item/7553/toc/368665 , accessed on June 18, 2024.
United States. Bureau of the Census. "Composite Indexes," in United States. Bureau of the Census. "April 1971," Business Conditions Digest (April 1971) : 40-41. https://fraser.stlouisfed.org/title/43/item/7553/toc/368665 , accessed on June 18, 2024.