United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "May 1972," Business Conditions Digest (May 1972) : 103-104. https://fraser.stlouisfed.org/title/43/item/7566/toc/88855 , accessed on April 26, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "May 1972," Business Conditions Digest (May 1972) : 103-104. https://fraser.stlouisfed.org/title/43/item/7566/toc/88855 , accessed on April 26, 2024.