Columbia subject headings:
Fortification--Sweden--Gotland.
Gotland (Sweden)--Antiquities.
Torsburgen Site (Sweden)
Vikings--Sweden--Gotland.
Harvard subject headings:
Excavations (Archaeology)--Sweden--Gotland.
Fortification, Prehistoric--Sweden--Gotland.
Gotland (Sweden)--Antiquities.
Sweden--Antiquities.
Princeton subject headings: