Columbia subject headings:
Harvard subject headings:
Agriculture--Economic aspects--Indonesia--Sumatera Timur.
Plantations--Indonesia--Sumatera Timur.
Rubber industry and trade--Indonesia--Sumatera Timur.
Sumatera Timur (Indonesia)--History.
Princeton subject headings:
Agriculture--Economic aspects--Indonesia--Sumatera Timur.
Plantations--Indonesia--Sumatera Timur.
Rubber industry and trade--Indonesia--Sumatera Timur.
Sumatera Timur--History.