Silverman, David, author
Sage Publications , 2010
Buku Teks
Norman K. Denzin, Yvonna S. Lincoln, editors
Sage Publications, 2000
Buku Referensi
Silverman, David, author
Sage , 2013
Buku Teks
Neuman, Lawrence W., author
Pearson New International edition, 2014
Buku Teks
Berg, Bruce L. (Bruce Lawrence), 1954-, author
Pearson, 2014
Buku Teks