Columbia subject headings:
Bulgaria--Antiquities--Congresses.
Bulgaria--Civilization--Congresses.
Bulgarian philology--Congresses.
Folklore--Bulgaria--Congresses.
Harvard subject headings:
Bulgaria--History--Congresses.
Bulgaria--Social life and customs--Congresses.
Princeton subject headings:
Bulgaria--Antiquities--Congresses.
Bulgaria--Civilization--Congresses.
Bulgarian philology--Congresses.
Folklore--Bulgaria--Congresses.