Newman, Daniel
Routledge, 2007
Buku Referensi
Lane, Edward William
Frederick Ungar Publishing, 1956
Buku Referensi
Crystal, David, 1941-
Cambridge University Press, 1995
Buku Referensi
editor in chief Paul Procter
Cambridge University Press, 1995
Buku Referensi
Lutz, William D.
Cambridge University Press, 1994
Buku Referensi