United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1969," Business Conditions Digest (July 1969) : 49-51. https://fraser.stlouisfed.org/title/43/item/7532/toc/358104 , accessed on April 25, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1969," Business Conditions Digest (July 1969) : 49-51. https://fraser.stlouisfed.org/title/43/item/7532/toc/358104 , accessed on April 25, 2024.