Jane's Information Group, 1999
Buku Referensi
Whittaker, David J., author
Routledge, 2004
Buku Teks
edited by Abdul Rashid Moten and Noraini M. Noor
Thomson , 2007
Buku Teks
Karlina Helmanita, Irfan Abubakar and Dina Afrianty, editor
Universitas Islam Negeri Syarif Hidayatullah , 2004
Buku Teks
Coates, John 1
Westview Press, 1992
Buku Teks