Columbia subject headings:
Ireland--History--To 1172.
Scandinavia--History.
Vikings.
Harvard subject headings:
Ireland--Antiquities--Congresses.
Ireland--History--To 1172--Congresses.
Ireland--Relations--Scandinavia--Congresses.
Scandinavia--Antiquities--Congresses.
Scandinavia--Relations--Ireland--Congresses.
Vikings--Congresses.
Vikings--Ireland--Congresses.
Princeton subject headings:
Ireland--History--To 1172.
Scandinavia--History.
Vikings.