Foreign and Commonwealth Office
Her Majesty's Stationery Office, 1986
Buku Referensi
The Straits Times Press, 1971
Buku Teks
edited by Gillenwater, Jay Y., editor; Howards, Stuart S., editor
Mosby Year Book, 1990
Buku Referensi
Bagdade, John D., editor; Braverman, Lewis E., editor; Halter, Jeffrey B., editor; Horton, Edward S., editor; Kannan, C.R., editor
Bagdade, John D, 1990
Buku Referensi
Buku Teks