Cita APA (7th ed.)

Zimmermann, W. (1963). Nordrhein-Westfalen. Kröner.

Cita Chicago (17th ed.)

Zimmermann, Walther. Nordrhein-Westfalen. Stuttgart: Kröner, 1963.

Cita MLA (8th ed.)

Zimmermann, Walther. Nordrhein-Westfalen. Kröner, 1963.