translated by Tam Lye Suan
Director-General Department of Infomartion Malaysia, 2008
Buku Referensi
J.J. Raj
MPH Group, 2007
Buku Teks
Atterbury, Paul
Hurtwood Press, 1985
Buku Teks
National University of singapore, 2008
Majalah, Jurnal, Buletin
UN , 1999
Buku Teks