Baert, Patrick, author
Polity Press, 2005
Buku Teks
Pratt Vernon
Methuen Press, 1978
Buku Teks
Ryan, Alan
Oxford , 1970
Buku Teks
by Ronald A. Hardert ... [and others]
West Publishing, 1984
Buku Teks
Levison, Arnold B.
Pegasus, 1974
Buku Teks
Wisdom, J. O.
Avebury, 1987
Buku Teks