United States. Bureau of Labor Statistics. "Railroads," in United States. Bureau of Labor Statistics. "July 1987," PPI Detailed Report (July 1987) : 145-147. https://fraser.stlouisfed.org/title/63/item/21620/toc/36849 , accessed on April 19, 2024.
United States. Bureau of Labor Statistics. "Railroads," in United States. Bureau of Labor Statistics. "July 1987," PPI Detailed Report (July 1987) : 145-147. https://fraser.stlouisfed.org/title/63/item/21620/toc/36849 , accessed on April 19, 2024.