United States. Bureau of the Census. "Contents," in United States. Bureau of the Census. "April 1968," Business Conditions Digest (April 1968) : 3-4. https://fraser.stlouisfed.org/title/43/item/7250/toc/84827 , accessed on March 29, 2024.
United States. Bureau of the Census. "Contents," in United States. Bureau of the Census. "April 1968," Business Conditions Digest (April 1968) : 3-4. https://fraser.stlouisfed.org/title/43/item/7250/toc/84827 , accessed on March 29, 2024.