Potter, Pitman B.
University Of Washington Press, 1992
Buku Teks
Lewin, Pauline
Frederick A. Praeger, 1967
Buku Teks
Paolo Davide Farah, Elena Cima, editors
Routledge, 2016
Buku Teks
Heidemann, Maren
Springer, 2012
eBooks
Elliot, Catherine
Longman , 2001
Buku Teks