edited by Michael Pacione
Barnes & Noble Books, 1983;1983;1983;1983;1983;1983
Buku Teks SO
Woods, Michael
Sage, 2012
eBooks
Clout, Hugh D.
Pergamon Press, 1977
Buku Teks SO
edited by D.T. Herbert and R.J. Johnston
John Wiley & Sons, 1978
Buku Teks SO
Getis, Arthur
McGraw-Hill, 2000
Buku Teks SO