APA (7th ed.) Citation

(1949). The Ruhr Area: Its strucure and economic importance. US-Govt. Print. Off.

Chicago Style (17th ed.) Citation

The Ruhr Area: Its Strucure and Economic Importance. Washington: US-Govt. Print. Off, 1949.

MLA (9th ed.) Citation

The Ruhr Area: Its Strucure and Economic Importance. US-Govt. Print. Off, 1949.