edited by Geoffrey Walford
Falmer Press, 1998
Buku Teks
McLeod, John
Sage Publications , 2003
Buku Teks
Molly Andrews, Corinne Squire, Maria Tamboukou, editor
Sage, 2009
Buku Teks SO
Crouch, Christopher
Berg, 2012
Buku Teks SO
Johnson, John M.
The Free Press, 1975
Buku Teks SO