Columbia subject headings:
Language and languages--Variation--Congresses.
Slavic languages--Standardization--Congresses.
Slavic languages--Variation--Congresses.
Standard language--Congresses.
Harvard subject headings:
Language and languages--Variation--Congresses
Slavic languages--Standardization--Congresses.
Slavic languages--Variation--Congresses.
Standard language--Congresses.
Princeton subject headings: