edited by Michael Pacione.
Barnes & Noble Books, [1983;1983;1983;1983;1983, 1983]
Buku Teks
Woods, Michael
Sage Publications, 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
Getis, Arthur
McGraw-Hill, 2000
Buku Teks