Warr, George, author
Sweet & Maxwell, 1994
Buku Teks
edited by Barry Turner
Macmillan and The Free Press, 1992
Buku Referensi
Phelan, Margaret
Blakstone Press Limited, 1997
Buku Teks
Trevithick, Pamela, author
McGraw-Hill , 2012
Buku Teks
Routledge , 1994
Buku Teks