United States. Bureau of Labor Statistics. "Employment Status of the Noninstitutional Population by Age and Sex," in United States. Bureau of Labor Statistics. "December 1973 : Industry Statistics and Annual Review," The Employment Situation (January 11, 1974) : 11-11. https://fraser.stlouisfed.org/title/144/item/497002/toc/512536 , accessed on April 25, 2024.