TAS-11Ltd, 1994
Buku Referensi
Longman Community Information
Longman Grup, 1994
Buku Referensi
edited by J.F. Burnet
A & C Black, 1987
Buku Referensi
by Robert Chia, Marzuki Usman, Suyanto Gondokusumo and Wong Kwei Cheong
Prentice-Hall, 1992
Buku Teks
Cooper, Geoffrey
Butterworth, 1971
Buku Teks