MLA

of Strategic Services. Geography Division, United States. Office. Spain and Portugal Hypsometric Map [Cartographic Material] / Compiled and Drawn in Geography Division, O.S.S. OSS, 1942. https://collections.library.yale.edu/catalog/15487316.

APA, 6th edition

of Strategic Services. Geography Division, U. S. O. (1942). Spain and Portugal hypsometric map [cartographic material] / compiled and drawn in Geography Division, O.S.S. [Maps]. OSS, https://collections.library.yale.edu/catalog/15487316.