Donaldson, Cam, author
Macmillan, 1994
Buku Teks
Phelps, Charles E., author
Harper Collins, 1992
Buku Teks
Abel-Smith, Brian
Heinemann, 1983
Buku Teks
Cooper, Michael H., author
John Wiley & Sons, 1975
Buku Teks
Wonderling, David, author
Open University Press, 2005
Buku Teks