Columbia subject headings:
Harvard subject headings:
Cities and towns--Austria--Vienna--Congresses.
Cities and towns--Danube River Valley--Congresses.
Cities and towns--Hungary--Budapest--Congresses.
City planning--Danube River Valley--Congresses.
Danube River Valley--Social conditions--Congresses.
Urbanization--Danube River Valley--Congresses.
Princeton subject headings:
Cities and towns--Austria--Vienna--Congresses.
Cities and towns--Danube River Valley--Congresses.
Cities and towns--Hungary--Budapest--Congresses.
City planning--Danube River Valley--Congresses.
Danube River Valley--Social conditions--Congresses.
Urbanization--Danube River Valley--Congresses.