United States. Bureau of Labor Statistics. "Producer Price Indexes by Durability of Product, Not Seasonally Adjusted," in United States. Bureau of Labor Statistics. "June 2007 (Corrected)," PPI Detailed Report (June 2007) : 141-141. https://fraser.stlouisfed.org/title/63/item/21859/toc/165927 , accessed on March 28, 2024.