United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1981," Business Conditions Digest (July 1981) : 80-83. https://fraser.stlouisfed.org/title/43/item/7419/toc/226073 , accessed on March 29, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1981," Business Conditions Digest (July 1981) : 80-83. https://fraser.stlouisfed.org/title/43/item/7419/toc/226073 , accessed on March 29, 2024.