Columbia subject headings:
Harvard subject headings:
Istituto internazionale per lo studio del problema delle classi medie--History.
Middle class--History--20th century.
Sociology--Europe--History--20th century.
Princeton subject headings:
Istituto internazionale per lo studio del problema delle classi medie--History.
Middle class--History--20th century.
Sociology--Europe--History--20th century.