Routledge, 1992
Buku Teks
Hall, Rodney
McPhee Gribble , 1988
Buku Teks
Robbins, Lionel Robbins, Baron, 1898-1984, editor
Macmilan Co., 1936
Buku Teks
Davidson, Lionel
Oxford University Press, 1980
Buku Teks
Lacey, Nicola, author
Oxford University Press, 2006
Buku Teks