Sophie Laws, Caroline Harper, Nicola JOnes, Rachel Marcus
SAGE, 2013
Buku Teks
Denscombe, Martyn
Open University Press, 2012
Buku Teks
Oades, Lindsay G.
Sage, 2019
Buku Teks
edited by Janet Holmes and Kirk Hazen
John Wiley & Sons, 2014
Buku Teks SO
Weirich, Thomas
South-Western, 1988
Buku Teks SO