Columbia subject headings:
Amazon River Region--Economic conditions--Congresses.
Amazon River Region--Social conditions--Congresses.
Brazil, Northeast--Economic conditions--Congresses.
Brazil, Northeast--Social conditions--Congresses.
Tropics--Economic conditions--Congresses.
Tropics--Social conditions--Congresses.
Harvard subject headings:
Amazon River Region--Economic conditions--Congresses.
Amazon River Region--Social conditions--Congresses.
Brazil, Northeast--Economic conditions--Congresses.
Brazil, Northeast--Social conditions--Congresses.
Tropics--Economic conditions--Congresses.
Tropics--Social conditions--Congresses.
Princeton subject headings:
Amazon River Valley--Congresses.
Brazil, Northeast--Congresses.
Tropics--Congresses.