Ball, Michael
Routledge , 1998
Buku Teks
Bailey, R.E.
Cambridge University Press, 2005
Buku Teks
Boyes, William J.
South Western Cengage Learning, 2012
Buku Teks
Townsend, Harry
Routledge , 1995
Buku Teks
Dipasquale, Denise
Prentice-Hall, 1996
Buku Teks