United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1989," Business Conditions Digest (July 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7515/toc/331927 , accessed on April 25, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1989," Business Conditions Digest (July 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7515/toc/331927 , accessed on April 25, 2024.