United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1987," Business Conditions Digest (June 1987) : 80-83. https://fraser.stlouisfed.org/title/43/item/7490/toc/321733 , accessed on May 4, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "June 1987," Business Conditions Digest (June 1987) : 80-83. https://fraser.stlouisfed.org/title/43/item/7490/toc/321733 , accessed on May 4, 2024.