Kosters, Marvin H., author
American Enterprise Institute for Public Policy Research, 1975
Buku Teks
MacIver, Robert M., author
Alfred A. Knopf, 1952
Buku Teks
Prodist, 1973
Buku Teks
Lyon, Leverett S., author
The Brookings Institution, 1940
Buku Teks
Colorado Westvies Press, Inc., 1982
Buku Teks