Cullen, Pauline, author
Cambridge university press, 2010
Buku Teks
Bauer, Lauria
London : Routledge, 1998
Buku Teks
Morgan, John, 1944-2004, author
Oxford University Press, 1990
Buku Teks
Hopkins, Diana, author
Cambridge University Press, 2011
Buku Teks
Buku Teks