APA (7th ed.) Citation

United States. Bureau of Mines. (1939). Some signaling systems in metal-­mine shafts. [s.n.].

Chicago Style (17th ed.) Citation

United States. Bureau of Mines. Some Signaling Systems in Metal-­mine Shafts. [Washington]: [s.n.], 1939.

MLA (9th ed.) Citation

United States. Bureau of Mines. Some Signaling Systems in Metal-­mine Shafts. [s.n.], 1939.