Use logical keywords to identify several relevant records, then look at the full record to determine if there are Subject Headings that might expand your search.
Keyword search: japanese american internment
Subject Headings: Japanese Americans -- Evacuation and relocation, 1942-1945.
Potentially Useful Subject Headings:
Concentration camps -- United States. [not restricted to Japanese Americans]
Japanese Americans -- Evacuation and relocation, 1942-1945 correspondence [subject keywords]
World War, 1939-1945 -- Reparations Japanese Americans [subject keywords]