United States. Bureau of Labor Statistics. "Wage Chronology: Bituminous Coal Mine Operators and United Mine Workers, 1933-81 : Bulletin of the United States Bureau of Labor Statistics, No. 2062," Wage Chronology: Bituminous Coal Mine Operators and United Mine Workers of America (1980). https://fraser.stlouisfed.org/title/4650/item/499621, accessed on December 20, 2024.