United States. Bureau of Labor Statistics. "Employed and Unemployed Persons by Occupation, Not Seasonally Adjusted," in United States. Bureau of Labor Statistics. "April 2007," The Employment Situation (May 4, 2007) : 14-14. https://fraser.stlouisfed.org/title/144/item/494801/toc/508398 , accessed on May 1, 2024.