Columbia subject headings:
Racism--History--20th century.
Revolutions--History--20th century.
Social change--History--20th century.
Harvard subject headings:
Racism--History--20th century.
Revolutions--History--20th century
Social change--History--20th century.
Princeton subject headings:
Racism--History--20th century.
Revolutions--History--20th century.
Social change--History--20th century.