United States. Bureau of Labor Statistics. "Railroads," in United States. Bureau of Labor Statistics. "July 1988," PPI Detailed Report (July 1988) : 138-139. https://fraser.stlouisfed.org/title/63/item/21632/toc/109876 , accessed on April 19, 2024.
United States. Bureau of Labor Statistics. "Railroads," in United States. Bureau of Labor Statistics. "July 1988," PPI Detailed Report (July 1988) : 138-139. https://fraser.stlouisfed.org/title/63/item/21632/toc/109876 , accessed on April 19, 2024.