United States. Bureau of Labor Statistics. "Employment, Hours, and Earnings, States and Areas, 1972-87 : Volume II: Illinois-Michigan : Bulletin of the United States Bureau of Labor Statistics, No. 2320," Employment, Hours, and Earnings, States and Areas (March 1989). https://fraser.stlouisfed.org/title/245/item/5876/content/pdf/bls_eestates_1972to1987_v2, accessed on October 12, 2024.