Columbia subject headings:
Harvard subject headings:
Europe--Languages--History--Congresses.
Historical linguistics--Europe--Congresses.
Languages in contact--Europe--History--Congresses.
Princeton subject headings:
Historical linguistics--Congresses.
Indo-European languages--History--Congresses.
Indo-European philology--Congresses.
Language and culture--History--Congresses.
Language spread--Congresses.
Languages in contact--History--Congresses.