Columbia subject headings:
Harvard subject headings:
Oldenburg (Grand Duchy)--Foreign relations.
Oldenburg (Grand Duchy)--Politics and government--18th century.
Oldenburg (Grand Duchy)--Politics and government--19th century.
Peter Friedrich Ludwig, Duke of Oldenburg, 1755-1829--Political and social views.
Princeton subject headings:
Oldenburg (Grand Duchy)--Foreign relations.
Oldenburg (Grand Duchy)--Politics and government--18th century.
Oldenburg (Grand Duchy)--Politics and government--19th century.
Peter Friedrich Ludwig, Duke of Oldenburg, 1755-1829--Political and social views.