Jones, Daniel, author
Cambridge University Press, 2003
Buku Teks
Stone, Linton
Macmillan, 1967
Buku Teks
Ann-Marie Einhaus, editor
Cambridge University Press, 2016
Buku Teks
Peters, Pam, author
Cambridge University Press, 1995
Buku Referensi
Sampson, George, author
University Press, 1949
Buku Referensi