United States. Bureau of Labor Statistics. "National Compensation Survey: Occupational Earnings in the West North Central Census Division, June 2008 : Bulletin of the United States Bureau of Labor Statistics, No. 2728," National Compensation Survey: Occupational Earnings in the United States (August 2009). https://fraser.stlouisfed.org/title/6086/item/584787, accessed on August 2, 2024.