Columbia subject headings:
Labor unions--Organizing--United States--History--20th century.
Rubber industry workers--Labor unions--United States--History--20th century.
Harvard subject headings:
Labor unions--Organizing--United States--History--20th century.
Rubber industry workers--Labor unions--United States--History--20th century.
Princeton subject headings:
Labor unions--Organizing--United States--History--20th century.
Rubber industry workers--Labor unions--United States--History--20th century.