United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1984," PPI Detailed Report (August 1984) : 20-20. https://fraser.stlouisfed.org/title/63/item/21585/toc/220372 , accessed on April 23, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "August 1984," PPI Detailed Report (August 1984) : 20-20. https://fraser.stlouisfed.org/title/63/item/21585/toc/220372 , accessed on April 23, 2024.