APA (7th ed.) Citation

United States. Bureau of Standards. (1939). Specification for proving rings for calibrating testing machines. [s.n.].

Chicago Style (17th ed.) Citation

United States. Bureau of Standards. Specification for Proving Rings for Calibrating Testing Machines. [Washington]: [s.n.], 1939.

MLA (9th ed.) Citation

United States. Bureau of Standards. Specification for Proving Rings for Calibrating Testing Machines. [s.n.], 1939.

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