United States. Bureau of the Census. "Leading Indicators," in United States. Bureau of the Census. "May 1968," Business Conditions Digest (May 1968) : 17-24. https://fraser.stlouisfed.org/title/43/item/7251/toc/131240 , accessed on April 24, 2024.
United States. Bureau of the Census. "Leading Indicators," in United States. Bureau of the Census. "May 1968," Business Conditions Digest (May 1968) : 17-24. https://fraser.stlouisfed.org/title/43/item/7251/toc/131240 , accessed on April 24, 2024.