United States. Bureau of the Census. "Composite Indexes," in United States. Bureau of the Census. "April 1981," Business Conditions Digest (April 1981) : 66-66. https://fraser.stlouisfed.org/title/43/item/7416/toc/419149 , accessed on July 15, 2024.
United States. Bureau of the Census. "Composite Indexes," in United States. Bureau of the Census. "April 1981," Business Conditions Digest (April 1981) : 66-66. https://fraser.stlouisfed.org/title/43/item/7416/toc/419149 , accessed on July 15, 2024.