United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1970," Business Conditions Digest (June 1970) : 95-97. https://fraser.stlouisfed.org/title/43/item/7543/toc/266731 , accessed on May 9, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1970," Business Conditions Digest (June 1970) : 95-97. https://fraser.stlouisfed.org/title/43/item/7543/toc/266731 , accessed on May 9, 2024.