United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1970," Business Conditions Digest (July 1970) : 86-87. https://fraser.stlouisfed.org/title/43/item/7544/toc/187215 , accessed on April 23, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1970," Business Conditions Digest (July 1970) : 86-87. https://fraser.stlouisfed.org/title/43/item/7544/toc/187215 , accessed on April 23, 2024.