Peck, Anthony
MacMillan,, 1995
Buku Teks
Donaldson, Bruce, author
Routledge, 2004
Buku Referensi
Saunders, Joy, author
Pearson Education, 1994
Buku Teks
Coggle, Paul, author
Teach Youeself Books, 1991
Buku Teks
Miell, Anna, author
Routledge, 2006
Buku Teks