Routledge in association with the Open University, 2006
Buku Teks SO
Sawahata, Lesa
Rockport, 2001
Buku Teks SO
Smoke, Trudy, editor
Cambridge University Press,, 2006
Buku Teks SO
edited by Max S. Wortman
Allyn and Bacon , 1970
Buku Teks
Pressat, Roland
Methuen, 1966
Buku Teks SO