Graziano, Anthony M., author
Pearson Education, 2014
Buku Teks
Pertti J, Pelto, author
Cambridge University Press, 2012
eBooks
New jersey, 2004
Buku Teks
edited by Peter Reason, Hilary Bradbury
Sage , 2013
Buku Referensi
Deming, M. Elen, author
John Wiley & Sons, 2011
Buku Teks