United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "March 1975," Business Conditions Digest (March 1975) : 91-91. https://fraser.stlouisfed.org/title/43/item/7343/toc/63857 , accessed on April 26, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "March 1975," Business Conditions Digest (March 1975) : 91-91. https://fraser.stlouisfed.org/title/43/item/7343/toc/63857 , accessed on April 26, 2024.