Jordan, Peter, author
Gower , 1995
Buku Teks
Jones, Noragh, author
Gower, 1987
Buku Teks
Jordan, Peter, author
Ashgate, 2002
Buku Teks
Clements, John, 1946-, author
John Wiley & Sons, 1994
Buku Teks
Griffin, Ricky W., author
Houghton Miffiln, 1990
Buku Teks