United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1987," Business Conditions Digest (July 1987) : 80-82. https://fraser.stlouisfed.org/title/43/item/7491/toc/293409 , accessed on March 19, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1987," Business Conditions Digest (July 1987) : 80-82. https://fraser.stlouisfed.org/title/43/item/7491/toc/293409 , accessed on March 19, 2024.