United Nations Departemen of Public Information, 1990
Buku Teks
Frieden, Jeffry A., author
Thomson Wadsworth, 2000
Buku Teks
Abbott, Lawrence, author
Harcourt, Brace and World, 1967
Buku Teks
Commons, John R.
Macmillan, 1934
Buku Teks
Daugherty, Carroll R.
Houghton Miffiln, 1950
Buku Teks