Mill, John Stuart
Colonial Press, 1898
Buku Klasik
Daughterty, Caroll R., author
Houghton Mifflin, 1950
Buku Teks
Commons, John R.
Macmillan, 1934
Buku Teks
Daugherty, Carroll R.
Houghton Miffiln, 1950
Buku Teks
Lieberman, Marc, author
South-Wetern & Cengage Learning, 2013
Buku Teks