Columbia subject headings:
Language policy--Congresses.
Languages in contact--Congresses.
Sociolinguistics--Congresses.
Harvard subject headings:
Language policy--Congresses.
Languages in contact--Congresses.
Sociolinguistics--Congresses.
Princeton subject headings:
Language policy--Congresses.
Languages in contact--Congresses.
Sociolinguistics--Congresses.