Walker, Robert A.
Dryden Press, 1953
Buku Teks SO
Baber, Anne
American Management Association, 2007
eBooks
Babbie, Earl R.
Wadsworth and Cengage Learning, 2013 (Student Edition)
Buku Teks SO
Babbie, Earl R.
Wadsworth and Cengage Learning, 2013 (International edition)
Buku Teks SO
Posner, Richard A.
Harvard University Press , 1988
Buku Teks