Medhurst, David, author
Blackwell Scientific Publications, 1994
Buku Referensi
Akester, Patricia, author
Sweet & Maxwel, [Date of publication not identified]
Buku Teks
Shilling, Dana, author
Prentice-Hall, 1998
Buku Referensi
Schwartz, Mortimer D., author
Gale Research, 1977
Buku Teks
Stubbs, Amanda, author
Thomas Telford, 1998
Buku Teks