Bulgaria [cartographic material] : administrative divisions / compiled and drawn in the Branch of Research and Analysis, OSS.
MLA
of Strategic Services. Research, United States. Office, and Analysis Branch. Bulgaria [Cartographic Material] : Administrative Divisions / Compiled and Drawn in the Branch of Research and Analysis, OSS. Reproduction Branch, OSS, 1943. https://collections.library.yale.edu/catalog/15498825.
APA, 6th edition
of Strategic Services. Research, U. S. O., & Branch, A. (1943). Bulgaria [cartographic material] : administrative divisions / compiled and drawn in the Branch of Research and Analysis, OSS. [Maps]. Reproduction Branch, OSS, https://collections.library.yale.edu/catalog/15498825.