APA (7th ed.) Citation

Paul, J. W. (1927). Area of unsupported roof in coal mines; conditions and factors for consideration. [publisher not identified].

Chicago Style (17th ed.) Citation

Paul, J. W. Area of Unsupported Roof in Coal Mines; Conditions and Factors for Consideration. Washington, D.C.: [publisher not identified], 1927.

MLA (9th ed.) Citation

Paul, J. W. Area of Unsupported Roof in Coal Mines; Conditions and Factors for Consideration. [publisher not identified], 1927.