United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "July 1985," PPI Detailed Report (July 1985) : 16-17. https://fraser.stlouisfed.org/title/63/item/21596/toc/223989 , accessed on April 25, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "July 1985," PPI Detailed Report (July 1985) : 16-17. https://fraser.stlouisfed.org/title/63/item/21596/toc/223989 , accessed on April 25, 2024.