United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "April 1977," Business Conditions Digest (April 1977) : 43-45. https://fraser.stlouisfed.org/title/43/item/7368/toc/49202 , accessed on May 4, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "April 1977," Business Conditions Digest (April 1977) : 43-45. https://fraser.stlouisfed.org/title/43/item/7368/toc/49202 , accessed on May 4, 2024.