Columbia subject headings:
Harvard subject headings:
Amazon River Valley--Civilization.
Brazil, Northeast--Civilization.
Rubber industry and trade--Amazon River Valley--History--19th century.
Rubber industry and trade--Brazil, Northeast--History--19th century.
Princeton subject headings:
Amazon River Valley--Civilization.
Brazil, Northeast--Civilization.
Rubber industry and trade--Amazon River Valley--History--19th century.
Rubber industry and trade--Brazil, Northeast--History--19th century.