APA (7th ed.) Citation

United States. Bureau of Mines. (1921). Precautions to be observed in entering abandoned exploratory shafts and pits. [publisher not identified].

Chicago Style (17th ed.) Citation

United States. Bureau of Mines. Precautions to Be Observed in Entering Abandoned Exploratory Shafts and Pits. [Washington]: [publisher not identified], 1921.

MLA (9th ed.) Citation

United States. Bureau of Mines. Precautions to Be Observed in Entering Abandoned Exploratory Shafts and Pits. [publisher not identified], 1921.

Warning: These citations may not always be 100% accurate.