Columbia subject headings:
Friends of the library--Germany--Berlin--History--20th century.
Libraries--Germany--Berlin--Societies, etc.--History--20th century.
Verein der Freunde der Preussischen Staatsbibliothek--History--20th century.
Harvard subject headings:
Friends of the library--Germany--Berlin--History--20th century.
Libraries--Germany--Berlin--Societies, etc.--History--20th century.
Verein der Freunde der Preussischen Staatsbibliothek--History--20th century.
Princeton subject headings: