Columbia subject headings:
Bonn (Germany)--History.
Bonn Region (Germany)--History.
Dietz, Josef--Bibliography.
Harvard subject headings:
Bonn (Germany)--History.
Bonn Region (Germany)--History.
Dietz, Josef--Bibliography.
Princeton subject headings:
Bonn (Germany)--History.
Bonn Region (Germany)--History.
Dietz, Josef--Bibliography.