Cite

Ordnance Survey of Great Britain [cartographic material] : England & Wales.

MLA

Survey, Great Britain. Ordnance. Ordnance Survey of Great Britain [Cartographic Material] : England & Wales. Ordnance Survey, 1940. https://collections.library.yale.edu/catalog/15832226.

APA, 6th edition

Survey, G. B. O. (1940). Ordnance Survey of Great Britain [cartographic material] : England & Wales. [Maps, Topographic maps]. Ordnance Survey, https://collections.library.yale.edu/catalog/15832226.