Armstrong, Michael
Bhuana Ilmu Populer, 2003
Buku Teks
Dale, Margaret
Crest Publishing House, 1999
Buku Referensi
Armstrong, Michael
Kogan Page, 2001
Buku Teks
Armstrong, Michael
Kogan Page, 2001
Buku Teks
Armstrong, Michael
[Publisher not identified], [Date of publication not identified]
Buku Teks