United States. Bureau of Labor Statistics. "Illinois," in United States. Bureau of Labor Statistics. "Employment Hours, and Earnings, States and Areas, Data for 1987-92 : Bulletin of the United States Bureau of Labor Statistics, No. 2411," Employment, Hours, and Earnings, States and Areas (August 1992) : 175-200. https://fraser.stlouisfed.org/title/245/item/5877/toc/332169 , accessed on April 19, 2024.