APA (7th ed.) Citation

Harris, C. D. (1943). [Maps of the Ruhr]. s.n.].

Chicago Style (17th ed.) Citation

Harris, Chauncy D. [Maps of the Ruhr]. [Chicago: s.n.], 1943.

MLA (8th ed.) Citation

Harris, Chauncy D. [Maps of the Ruhr]. s.n.], 1943.