Page, Malcolm, author
Macmillan Education, 1987
Buku Teks
Schechner, Richard, author
Routledge, 2013
Buku Teks
Boyatzis, Richard E.
John Wiley & Sons, 1982
Buku Teks
Cambridge University Press, 1993
eBooks
Cave, Richard Allen
Macmillan Education, 1988
Buku Teks