MLA

Section, Great Britain. War Office. General Staff. Geographical. North-East Frontier of France [Cartographic Material]. Ordnance Survey, 0AD. https://collections.library.yale.edu/catalog/15484157.

APA, 6th edition

Section, G. B. W. O. G. S. G. (0 C.E.). North-east frontier of France [cartographic material]. [Maps]. Ordnance Survey, https://collections.library.yale.edu/catalog/15484157.