To search for a subject when the terminology is not known, first search by keyword, then look for relevant records and, using the full record of a book, see if there are any relevant Library of Congress Subject Headings (LCSH) to further your search.
Keyword Search: new deal encyclopedias
LCSH: New Deal, 1933-1939 -- Encyclopedias.
United States -- Social conditions -- 1933-1945
United States -- Economic conditions -- 1918-1945
Library of Congress Subject Headings (provided by UNC Wilson Library Special Collections):
This Library of Congress Classification Outline holds true for any library in the world using the LC system. For example, British literature will be classed in the PRs & American Literature is classed in the PSs.