United States. Bureau of the Census. "Contents," in United States. Bureau of the Census. "January 1968," Business Conditions Digest (January 1968) : 3-4. https://fraser.stlouisfed.org/title/43/item/7247/toc/394247 , accessed on April 18, 2024.
United States. Bureau of the Census. "Contents," in United States. Bureau of the Census. "January 1968," Business Conditions Digest (January 1968) : 3-4. https://fraser.stlouisfed.org/title/43/item/7247/toc/394247 , accessed on April 18, 2024.