Wiyogo P. Wicaksono
Universitas Indonesia, 2014
Artikel Jurnal
Neuman, Lawrence W.
Pearson New International edition, 2014
Buku Teks
Creswell, John W.
Sage, 1994
Buku Teks SO
Neuman, William Lawrence, 1950-
Allyn and Bacon, 2003
Buku Teks
Punch, Keith F.
Sage, 1998
Buku Teks