Columbia subject headings:
Harvard subject headings:
Scandinavia--History--To 1500--Congresses.
Slave traders--Scandinavia--History--To 1500--Congresses.
Slavery--Scandinavia--History--To 1500--Congresses.
Vikings--Scandinavia--History--To 1500--Congresses.
Vikings--Scandinavia--Social life and customs--Congresses.
Princeton subject headings:
Slavery--Scandinavia--History.
Vikings--Social life and customs.