Williams, Lea E.
Oxford University Press, Inc, 1976
Buku Teks
King, John Kerry, author
Macmillan, 1959
Buku Teks
ASEAN Focus Group ; edited by Peter Church
Allen & Unwin, 1995
Buku Teks
Bastin, John, author
Prentice Hall of Australia, 1977
Buku Teks
Progressio, 1972
Buku Teks