Author,Title,Edition,Publisher,Year,Series,Number,ISBN,ISSN,URL
"Barger, Harold and Schurr, Sam H.","The mining industries, 1899-1939 : a study of output, employment and productivity",,University Microfilms,1944,"Publications of the National Bureau of Economic Research, Incorporated",,,,https://cir.nii.ac.jp/crid/1130282269200572672