United States. Bureau of Labor Statistics. "Employment Projections: 2006-16 : Release, USDL 07-1847,"
Economic and Employment Projections and Occupational Outlook Handbook
(December 4, 2007).
https://fraser.stlouisfed.org/title/9639/item/707050/content/pdf/ecopro_20071204, accessed on June 9, 2026.