United States. Bureau of Labor Statistics. "Labor Requirements for Construction Materials. Pt. I—Portland Cement : Bulletin of the United States Bureau of Labor Statistics, No. 888-1" in Labor Requirements for Construction Materials : Bulletin of the United States Bureau of Labor Statistics, No. 888 (1947). https://fraser.stlouisfed.org/title/4343/item/495025, accessed on November 18, 2024.