United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "April 1989," Business Conditions Digest (April 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7512/toc/317186 , accessed on May 16, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "April 1989," Business Conditions Digest (April 1989) : 44-46. https://fraser.stlouisfed.org/title/43/item/7512/toc/317186 , accessed on May 16, 2024.