Columbia subject headings:
Oldenburg (Germany)--History--17th century.
Postage stamps--Germany--Oldenburg--History--19th century.
Postage stamps--Germany--Oldenburg--Pictorial works.
Postal service--Germany--Oldenburg--History--19th century.
Harvard subject headings:
Oldenburg (Germany)--History--17th century.
Postage stamps--Germany--Oldenburg--History--19th century.
Postage stamps--Germany--Oldenburg--Pictorial works.
Postal service--Germany--Oldenburg--History--19th century.
Princeton subject headings:
Oldenburg (Germany)--History--17th century.
Postage stamps--Germany--Oldenburg--History--19th century.
Postage stamps--Germany--Oldenburg--Pictorial works.
Postal service--Germany--Oldenburg--History--19th century.