United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1975," Business Conditions Digest (June 1975) : 56-57. https://fraser.stlouisfed.org/title/43/item/7346/toc/263740 , accessed on June 22, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1975," Business Conditions Digest (June 1975) : 56-57. https://fraser.stlouisfed.org/title/43/item/7346/toc/263740 , accessed on June 22, 2024.