Gilliam, Ronald B.
Jones and Bartlett Publishers, 2011
Multimedia
Gelfer, Marylou Pausewang
McGraw-Hill, 1996
Buku Teks
Cummings, Louise
Cambridge University Press, 2016
Buku Teks
edited by Shelagh Brumfitt
Wiley - Blackwell, 2010
Buku Teks
edited by Jack S. Damico, Nicole Muller and Martin J. Ball
Wiley-Blackwell, 2013
Buku Teks