United States. Bureau of the Census. "April 1968," Business Conditions Digest (April 1968). https://fraser.stlouisfed.org/title/43/item/7250, accessed on April 17, 2024.
United States. Bureau of the Census. "April 1968," Business Conditions Digest (April 1968). https://fraser.stlouisfed.org/title/43/item/7250, accessed on April 17, 2024.