Columbia subject headings:
Agriculture--Economic aspects--Amazon River Region--Congresses.
Amazon River Region--Commerce--Congresses.
Rubber industry and trade--Amazon River Region--Congresses.
Harvard subject headings:
Agriculture--Brazil--Amazonas--Congresses.
Amazonas (Brazil)--Commerce--Congresses.
Amazonas (Brazil)--Economic conditions--Congresses.
Rubber industry and trade--Brazil--Amazonas--Congresses.
Rubber--Brazil--Amazonas--Congresses.
Princeton subject headings:
Agriculture--Economic aspects--Amazon River Region--Congresses.
Amazon River Region--Commerce--Congresses.
Rubber industry and trade--Amazon River Region--Congresses.