Longman Singapore Publishers , 1990
Buku Teks
The Government of Singapore, 1991
Buku Teks
Asrinda, author
Fakultas Ilmu Pengetahuan dan Budaya Universitas Indonesia, 2006
UI - Skripsi (Membership)
Foreign office of the federal Republic of Germany , 1982
Buku Teks
New York Oxford University Press 1970,
Buku Teks