United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1988," Business Conditions Digest (July 1988) : 44-46. https://fraser.stlouisfed.org/title/43/item/7503/toc/420496 , accessed on April 24, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1988," Business Conditions Digest (July 1988) : 44-46. https://fraser.stlouisfed.org/title/43/item/7503/toc/420496 , accessed on April 24, 2024.