Sofiya : North K 34. / 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. Sofiya : North K 34. / compiled at the Royal Geographical Society under the direction of the Geographical Section; drawn and printed by Ordnance Survey.. BRBL_00010ZA. 1918. https://collections.library.yale.edu/catalog/15238292.
APA, 6th edition
Ordnance Survey of Great Britain and Ireland, & Royal Geographical Society (Great Britain). Geographical Section. (["BRBL_00010ZA"])(1918)[Sofiya : North K 34. / 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/15238292.
