This primary source comes from the Records of the Central Intelligence Agency.
Full Citation: U.S.S.R. - Ethnic Compositions; 7/1949; Published Maps, 1947 - 2015; Records of the Central Intelligence Agency, Record Group 263; National Archives at College Park, College Park, MD. [Online Version, https://docsteach.org/documents/document/ussr-ethnic-compositions, September 9, 2024]