Daughterty, Caroll R., author
Houghton Mifflin, 1950
Buku Teks
Daugherty, Carroll R.
Houghton Miffiln, 1950
Buku Teks
Mill, John Stuart
Colonial Press, 1898
Buku Klasik
Case, Karl E., author
Pearson, Prentice Hall, 2009
Buku Teks
Mankiw, N. Gregory, author
Harcout College, 1998
Buku Teks