United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "April 1984," PPI Detailed Report (April 1984) : 13-13. https://fraser.stlouisfed.org/title/63/item/21581/toc/234053 , accessed on May 2, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "April 1984," PPI Detailed Report (April 1984) : 13-13. https://fraser.stlouisfed.org/title/63/item/21581/toc/234053 , accessed on May 2, 2024.