Salzmann, Zdenek, author
Westview Press, 998
Buku Teks
Roelofs, H. Mark
The Dorsey press, 1968
Buku Teks
Barber, Charles
Cambridge University Press, 1993
Buku Teks
Trudgill, Peter, author
Penguin, 1995
Buku Teks
Cruse, Alan, author
Oxford University Press, 2004
Buku Teks