Columbia subject headings:
Architecture--Conservation and restoration--Germany.
Fortification--Germany--Osnabrück.
Petersburg bei Osnabrück.
Harvard subject headings:
Architecture--Germany--Conservation and restoration.
Fortification--Germany--Osnabrück.
Petersburg bei Osnabrück.
Princeton subject headings:
Architecture--Germany--Conservation and restoration.
Fortification--Germany--Osnabrück.
Petersburg bei Osnabrück.