Daugherty, Carroll R.
Houghton Miffiln, 1950
Buku Teks
Commons, John R.
Macmillan, 1934
Buku Teks
Miller, Roger LeRoy, author
Pearson education, 2010
Buku Teks
Muller, Roger LeRoy, author
Addison-Wesley, 2000
Buku Teks
Robinson, Marshall A., author
Brookings Institution, 1955
Buku Teks