Kallen, Horace M.
Northern Illinois University Press, 1968
Buku Teks
Mill, John Stuart, author
David Campbell Publisher, 1992
Buku Referensi
Angus & Robertson , 1955
Buku Teks
Mohammad Shafil, author
Coriosita, 2004
Buku Teks
Brint, Michael, author
Westview Press, 1991
Buku Referensi