United States. Bureau of Labor Statistics. "Union Wages and Hours: Motortruck Drivers and Helpers, July 1, 1956 : Bulletin of the United States Bureau of Labor Statistics, No. 1206," Union Wages and Hours : Local Truckdrivers and Helpers (February 1957). https://fraser.stlouisfed.org/title/3960/item/495693, accessed on March 16, 2025.