United States. Bureau of the Census. "Series Finding Guide," in United States. Bureau of the Census. "May 1967," Business Conditions Digest (May 1967) : 87-89. https://fraser.stlouisfed.org/title/43/item/7239/toc/401970 , accessed on March 28, 2024.
United States. Bureau of the Census. "Series Finding Guide," in United States. Bureau of the Census. "May 1967," Business Conditions Digest (May 1967) : 87-89. https://fraser.stlouisfed.org/title/43/item/7239/toc/401970 , accessed on March 28, 2024.