United States. Bureau of Labor Statistics. Division of Construction and Public Employment and United States. Works Progress Administration. "East North Central Cities, Volume III" in Salaries and Hours of Labor in Municipal Police Departments, July 1, 1938 : Bulletin of the United States Bureau of Labor Statistics, No. 685 (1941). https://fraser.stlouisfed.org/scribd/?item_id=494407&filepath=/files/docs/publications/bls/bls_0685-v3_1941.pdf, accessed on November 23, 2017.