Roma : North K 33. / compiled at the Royal Geographical Society under the direction of the Geographical Section; drawn and printed by Ordnance Survey.
MLA
Ordnance Survey of Great Britain and Ireland, Royal Geographical Society (Great Britain). Geographical Section. Roma : North K 33. / compiled at the Royal Geographical Society under the direction of the Geographical Section; drawn and printed by Ordnance Survey.. 1916. https://collections.library.yale.edu/catalog/15238264.
APA, 6th edition
Ordnance Survey of Great Britain and Ireland, & Royal Geographical Society (Great Britain). Geographical Section. (1916)[Roma : North K 33. / compiled at the Royal Geographical Society under the direction of the Geographical Section; drawn and printed by Ordnance Survey.]. https://collections.library.yale.edu/catalog/15238264.