Columbia subject headings:
Labor unions--United States--Archival resources.
Socialism--United States--Archival resources.
Working class--United States--Archival resources.
Harvard subject headings:
Labor unions--United States--Archival resources.
Socialism--United States--Archival resources.
Working class--United States--Archival resources.
Princeton subject headings:
Labor movement--United States--Archival resources.
Labor unions--United States--Archival resources.
Socialism--United States--Archival resources.