United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "March 1989," Business Conditions Digest (March 1989) : 82-84. https://fraser.stlouisfed.org/title/43/item/7511/toc/386298 , accessed on May 7, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "March 1989," Business Conditions Digest (March 1989) : 82-84. https://fraser.stlouisfed.org/title/43/item/7511/toc/386298 , accessed on May 7, 2024.