Columbia subject headings:
Capitalism--United States--History--20th century.
Labor unions--United States--History--20th century.
Labor--United States--History--20th century.
Harvard subject headings:
Capitalism--United States--History--20th century.
Labor unions--United States--History--20th century
Labor--United States--History--20th century.
Princeton subject headings:
Capitalism--United States--History--20th century.
Labor unions--United States--History--20th century.
Labor--United States--History--20th century.