-
حسب Shedd, Solon, 1860-1941
منشور في 1924 -
Coal in Washington;distribution geology mining preparation uses and economic value of coal resources of WashingtonBookحسب Daniels, Joseph, 1884-1965
منشور في 1934 -
Report on the mining industries of the United States (exclusive of the precious metals)with special investigation into the iron resources of the republic and into the Cretaceous coals of the NorthwestBookحسب Pumpelly, Raphael, 1837-1923
منشور في 1886