Columbia subject headings:
Cities and towns--History--19th century--Congresses.
Cities and towns--History--20th century--Congresses.
Urbanization--History--19th century--Congresses.
Urbanization--History--20th century--Congresses.
Harvard subject headings:
Human geography--Congresses
Urbanization--History--19th century--Congresses.
Urbanization--History--20th century--Congresses.
Princeton subject headings:
Cities and towns.
Urbanization.