edited by Philip R. Cateora and Lee Richardson
Appleton-Century-Crofts, 1967
Buku Teks SO
Creswell, John W.
Sage, 1994
Buku Teks SO
Neuman, Lawrence W.
Pearson New International edition, 2014
Buku Teks SO
Napitupulu, Richard Bonardo
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2019
UI - Tesis Membership
Tashakkori, Abbas
Sage, 1998
Buku Teks SO