United States. Bureau of the Census. "Leading Indicators," in United States. Bureau of the Census. "April 1968," Business Conditions Digest (April 1968) : 59-59. https://fraser.stlouisfed.org/title/43/item/7250/toc/84844 , accessed on May 1, 2024.
United States. Bureau of the Census. "Leading Indicators," in United States. Bureau of the Census. "April 1968," Business Conditions Digest (April 1968) : 59-59. https://fraser.stlouisfed.org/title/43/item/7250/toc/84844 , accessed on May 1, 2024.