00329nam a2200109Ia 4500082002300000100003700023245008300060260002500143300001600168500000500184700003000189  a338.20973bB251.MI  aBarger, Harold and Schurr, S. H.  aMining industries, 1899, 1939; a study of output employment and productivityb  aNew YorkbNBERc1944  axxii, 452p.  a  aSchurr, S. H. ; jt. auth.