Columbia subject headings:
Harvard subject headings:
Berg (Duchy)--History--Congresses.
Peace of Westphalia--Congresses.
Thirty Years' War, 1618-1648--Congresses.
Princeton subject headings:
Berg (Duchy)--History--Congresses.
Peace of Westphalia--Congresses.
Thirty Years' War, 1618-1648--Congresses.