Columbia subject headings:
Language and languages--Variation--Congresses.
Languages in contact--Congresses.
Sign language--Congresses.
Harvard subject headings:
Language and languages--Variation--Congresses
Languages in contact--Congresses.
Sign language--Congresses
Princeton subject headings:
Language and languages--Variation--Congresses.
Languages in contact--Congresses.
Sign language--Congresses.