Sweet & Maxwell, 2011
Buku Teks
Gilmore, Glen, author
McGraw-Hill , 2015
Buku Teks
Wells, Walter
Kent Publishing Company, 1985
Buku Teks
edited and compiled by Mark Halloran
Prentice-Hall, 1991
Buku Teks
Calder, Alan, author
kogan page limited, 2005
Buku Teks