United States. Bureau of Labor Statistics. "Wage Chronology: Bituminous Coal Mines, 1933-66 : Bulletin of the United States Bureau of Labor Statistics, No. 1461,"
Wage Chronology: Bituminous Coal Mine Operators and United Mine Workers of America
(1965).
https://fraser.stlouisfed.org/title/4650/item/498056, accessed on April 11, 2025.
@FedFRASER