Cite

Bucuresti : North L 35. / 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. Bucuresti : North L 35. / compiled at the Royal Geographical Society under the direction of the Geographical Section; drawn and printed by Ordnance Survey.. 1918. https://collections.library.yale.edu/catalog/15238262.

APA, 6th edition

Ordnance Survey of Great Britain and Ireland, & Royal Geographical Society (Great Britain). Geographical Section. (1918)[Bucuresti : North L 35. / 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/15238262.