Cite

Ordnance Survey of Great Britain 1/4 inch to one mile.

MLA

Survey, Great Britain. Ordnance. Ordnance Survey of Great Britain 1/4 Inch to One Mile. 1920. https://collections.library.yale.edu/catalog/15832225.

APA, 6th edition

Survey, G. B. O. (1920). Ordnance Survey of Great Britain 1/4 inch to one mile. [Maps, Topographic maps]. https://collections.library.yale.edu/catalog/15832225.