United States. Bureau of Labor Statistics. "Employed and Unemployed Persons by Occupation, Not Seasonally Adjusted," in United States. Bureau of Labor Statistics. "December 2015," The Employment Situation (January 8, 2016) : 27-27. https://fraser.stlouisfed.org/title/144/item/521393/toc/514326 , accessed on May 8, 2024.