Skorupski, John
Routledge: Taylor & Francis Group, 2006
Buku Teks
Mill, John Stuart
David Campbell Publisher, 1992
Buku Referensi
Angus & Robertson , 1955
Buku Teks
Mill, John Stuart
Yayasan Obor Indonesia, 2005
Buku Teks
Mill, John Stuart
E.P. Dutton and Company, 1955
Buku Teks