"Electric blasting switches, underground mines, Lake Superior District."; "Cash, Frank E. (Frank Errette)", "Petersen, Max S."; "Mine safety--Lake States.", "Ground control (Mining)--Lake States.", "Iron mines and mining--Lake States--Safety measures."; "Petersen, Max S.", "Cash, Frank E. (Frank Errette)"; "1946"; "

Serial issue. Issued as: United States. Bureau of Mines. Information circular, 7372 (1946:Sept.).

"; ""; "P19460"; "pec"; "Ground control (Mining)--Lake States.", "Iron mines and mining--Lake States--Safety measures.", "Mine safety--Lake States."; "14256"; .