Murphy, Robert F.
Prentice-Hall, 1986
Buku Teks SO
Hammond, Peter
Macmillan, 1978
Buku Teks SO
Rapport, Nigel
Routledge, 2000
Buku Teks SO
Pennsylvania : University of Pittsburgh Press
Majalah, Jurnal, Buletin
Harris, Marvin, 1927-2001
HarperCollins, 1991
Buku Teks SO