edited by Ronan Paddison
Sage Publications, 2001
Buku Referensi
Bish, Robert L., author
McGraw-Hill Kogakusha, 1975
Buku Teks
edited by R.E. Pahl
Pergamon Press, 1968
Buku Teks
Mann, Peter H., author
Humanities Press, 1965
Buku Teks
Kennedy, Leslie W
McGraw-Hill Ryerson, 1983
Buku Teks