Farrell, Thomas S. C., author
Corwin Press, 2006
Buku Teks
Smith, Charles John, author
Bell and Sons, 1917
Buku Referensi
Artikel Jurnal
Burridge, Kate, author
Cambridge University Press, 2004
Buku Teks
Parrot, Martin, author
Cambridge University Press, 2003
Buku Teks