edited by Andrew Blowers, Bob Evans
Routledge, 1997
Buku Teks
Trident Press, [Date of publication not identified]
Buku Referensi
edited by Andrew Blowers and Bob Evans
Routledge, 1997
Buku Teks
edited by Philip Sutton and Hazel M. Mitchell
CABI, 2010
Buku Teks
Bernard, Miriam, author
Open University Press , 2000
Buku Teks