Lenkert, Erika, author
Macmillan, 2000
Buku Teks
edited by Alan Lightman
Houghtn Mifflin, 2000
Buku Teks
Artikel Jurnal
Chicago : encyclopaedia Britanica Inc, 2000,
Buku Referensi
Association of Southeast Asian Nations
ASEAN Secretariat, 2001
Buku Referensi