Doff, Adrian, author
Cambridge University Press , 2011
Buku Teks
Murphy, Raymond, author
Cambridge University Press, 1998
Buku Teks
Marsh, Philip Michael
Grasindo, 2007
Buku Teks
Tucker, T.G.
Macmillan, 1923
Buku Teks
Kaplan, Jeffrey P., author
Prentice Hall International, 1995
Buku Teks