"The Early history of the Pittsburgh Coal bed."; "Eavenson, Howard N. (Howard Nicholas), 1873-1953."; "Coal mines and mining--Pennsylvania--Pittsburgh."; "Eavenson, Howard N. (Howard Nicholas), 1873-1953."; "1939"; "Journal article tearout from: West Pennsylvania historical magazine, v.22:no.3(1939:Sept.)"; ""; "P1798"; "pec"; "Coal mines and mining--Pennsylvania--Pittsburgh."; "14256"; .