United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "May 1989," Business Conditions Digest (May 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7513/toc/331694 , accessed on May 9, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "May 1989," Business Conditions Digest (May 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7513/toc/331694 , accessed on May 9, 2024.