Aileen Kavanagh, John Oberdiek, editor
Routledge, 2009
Buku Teks
Stone, Richard, author
Cavendish Publishing Limited, 2000
Buku Teks
Mellor, J. Leigh
Teach Yourself Books, 1976
Buku Teks
Addison, Neil, author
Blackstone Press Limited, 1998
Buku Teks
Hegland, Kenney, author
St. Paul, Minn, 2003
Buku Teks