MLA

Section, Great Britain. War Office. General Staff. Geographical. Kiel Canal and Heligoland. War Office, 0AD. https://collections.library.yale.edu/catalog/15826915.

APA, 6th edition

Section, G. B. W. O. G. S. G. (0 C.E.). Kiel Canal and Heligoland. [Maps]. War Office, https://collections.library.yale.edu/catalog/15826915.