著者名,書名,版表示,出版者名,出版年,シリーズ名,番号,ISBN,ISSN,URL United States. Bureau of Labor Statistics,"Hours and earnings in anthracite and bituminous coal mining : anthracite-1919 and 1920, bituminous-1919",,U.S. G.P.O.,1921,Bulletin,,,,https://cir.nii.ac.jp/crid/1130282269248446336