United States. Bureau of the Census. "Series Finding Guide," in United States. Bureau of the Census. "May 1989," Business Conditions Digest (May 1989) : 116-119. https://fraser.stlouisfed.org/title/43/item/7513/toc/331742 , accessed on May 7, 2024.
United States. Bureau of the Census. "Series Finding Guide," in United States. Bureau of the Census. "May 1989," Business Conditions Digest (May 1989) : 116-119. https://fraser.stlouisfed.org/title/43/item/7513/toc/331742 , accessed on May 7, 2024.