United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1972," Business Conditions Digest (July 1972) : 52-53. https://fraser.stlouisfed.org/title/43/item/7568/toc/328461 , accessed on April 27, 2024.
United States. Bureau of the Census. "Diffusion Indexes," in United States. Bureau of the Census. "July 1972," Business Conditions Digest (July 1972) : 52-53. https://fraser.stlouisfed.org/title/43/item/7568/toc/328461 , accessed on April 27, 2024.