United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "February 1983," PPI Detailed Report (February 1983) : 13-13. https://fraser.stlouisfed.org/title/63/item/21567/toc/144819 , accessed on April 19, 2024.
United States. Bureau of Labor Statistics. "Coal," in United States. Bureau of Labor Statistics. "February 1983," PPI Detailed Report (February 1983) : 13-13. https://fraser.stlouisfed.org/title/63/item/21567/toc/144819 , accessed on April 19, 2024.