United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1989," Business Conditions Digest (June 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7514/toc/423557 , accessed on April 17, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1989," Business Conditions Digest (June 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7514/toc/423557 , accessed on April 17, 2024.