Columbia subject headings:
Harvard subject headings:
Celts--Congresses.
Celts--Germany--Congresses.
Celts--Rhine River Valley--Congresses.
Princeton subject headings:
Celtic philology--History--Congresses.
Celts--Germany--History--Congresses.
Celts--History--Congresses.
Celts--Rhine River Valley--History--Congresses.
Rhine River Valley--Antiquities, Celtic--Congresses.