Columbia subject headings:
Germany--History--1871-1918--Congresses.
Prussia (Germany)--History--1870---Congresses.
Harvard subject headings:
Germany--History--1871-1918--Congresses.
Prussia (Germany)--History--1870---Congresses.
Princeton subject headings:
Germany--History--1871-1918--Congresses.
Prussia (Germany)--History--1870---Congresses.