Chisholm, Roderick M., author
Prentice Hall International, 1989
Buku Teks
Morton, Adam, author
Blackwell, 1997
Buku Teks
O`Brien, Dan, author
Polity Press, 2006
Buku Teks
Barnes, Barry, author
Routledge & K. Paul, 1974
Buku Teks
Rescher, Nicholas, author
State University of New York Press, 2003
Buku Teks