Willett, Allan H. (Allan Herbert), 1865- and United States. Bureau of Labor Statistics. Industrial Survey in Selected Industries in the United States, 1919 : Bulletin of the United States Bureau of Labor Statistics, No. 265 , Washington: U.S. Govt. Print. Off., May 1920, https://fraser.stlouisfed.org/title/3908, accessed on March 9, 2025.