United States. Bureau of the Census. "December 1968," Business Conditions Digest (December 1968). https://fraser.stlouisfed.org/title/43/item/7525, accessed on April 19, 2024.
United States. Bureau of the Census. "December 1968," Business Conditions Digest (December 1968). https://fraser.stlouisfed.org/title/43/item/7525, accessed on April 19, 2024.