Bolkestein, Frits, author
Sumatra Institute, 2006
Buku Teks
Fagen, Richard R.
Calif Standford University Press, 1969.
Buku Teks
Lechner, Frank J., author
Blackwell, 2005
Buku Teks
Kaplan, David, author
Pustaka Pelajar, 1999
Buku Teks
Inglis, David, author
Routledge, 2005
Buku Teks