Columbia subject headings:
Forced labor--Putumayo River Valley--History--19th century.
Forced labor--Putumayo River Valley--History--20th century.
Indians, Treatment of--Putumayo River Valley--History--19th century.
Indians, Treatment of--Putumayo River Valley--History--20th century.
Rubber industry and trade--Putumayo River Valley--History--19th century.
Rubber industry and trade--Putumayo River Valley--History--20th century.
Harvard subject headings:
Forced labor--Putumayo River Valley--History--19th century.
Forced labor--Putumayo River Valley--History--20th century.
Indians, Treatment of--Putumayo River Valley--History--19th century.
Indians, Treatment of--Putumayo River Valley--History--20th century.
Rubber industry and trade--Putumayo River Valley--History--19th century.
Rubber industry and trade--Putumayo River Valley--History--20th century.
Princeton subject headings:
Forced labor--Putumayo River Valley--History--19th century.
Forced labor--Putumayo River Valley--History--20th century.
Indians, Treatment of--Putumayo River Valley--History--19th century.
Indians, Treatment of--Putumayo River Valley--History--20th century.
Rubber industry and trade--Putumayo River Valley--History--19th century.
Rubber industry and trade--Putumayo River Valley--History--20th century.