United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1983," PPI Detailed Report (August 1983) : 13-13. https://fraser.stlouisfed.org/title/63/item/21573/toc/277581 , accessed on April 24, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1983," PPI Detailed Report (August 1983) : 13-13. https://fraser.stlouisfed.org/title/63/item/21573/toc/277581 , accessed on April 24, 2024.