United States. Bureau of the Census. "Contents," in United States. Bureau of the Census. "May 1968," Business Conditions Digest (May 1968) : 3-4. https://fraser.stlouisfed.org/title/43/item/7251/toc/131233 , accessed on April 23, 2024.
United States. Bureau of the Census. "Contents," in United States. Bureau of the Census. "May 1968," Business Conditions Digest (May 1968) : 3-4. https://fraser.stlouisfed.org/title/43/item/7251/toc/131233 , accessed on April 23, 2024.