Mower, Alfred Glenn
Connecticut Greenwood Press 1979,
Buku Referensi
edited by Max F. Millikan
Little, Brown, 1961
Buku Teks
edited by Max F. Millikan and Donald L.M. Blackmer
Little, Brown, 1961
Buku Teks
The Academy of Political Science, 1977
Buku Teks
Derbyshire, Ian
Chambers, 1990
Buku Teks