Zweifel, Thomas D.
Communicate or die : Getting results through speaking and listening
Selectbooks, 2009
 Buku Teks SO
Schnitger, F.M.
Forgotten kingdoms in Sumatra
Oxford University Press, 1989
 Buku Teks
Schnitger, F.M.
Forgotten kingdoms in Sumatra
E.J. Brill, 1964
 Buku Teks
Woolley, Leonard, Sir
A Forgotten kingdom / Leonard Woolley
Penguin Books, 1953
 Buku Teks SO
Mossner, Ernest Campbell
The forgotten hume : le bon David
Columbia University Press, 1943
 Buku Teks SO