United States. Bureau of Labor Statistics. "Employed and Unemployed Persons by Occupation, Not Seasonally Adjusted," in United States. Bureau of Labor Statistics. "May 2012," The Employment Situation (June 1, 2012) : 25-25. https://fraser.stlouisfed.org/title/144/item/494862/toc/506797 , accessed on May 4, 2024.