Columbia subject headings:
Harvard subject headings:
Austria--In literature--Congresses.
Austria--Social life and customs--Congresses.
Bulgaria--In literature--Congresses.
Bulgaria--Social life and customs--Congresses.
Germany--In literature--Congresses.
Germany--Social life and customs--Congresses.
Princeton subject headings:
Austria--In literature--Congresses.
Austria--Social life and customs--Congresses.
Bulgaria--In literature--Congresses.
Bulgaria--Social life and customs--Congresses.
Germany--In literature--Congresses.
Germany--Social life and customs--Congresses.