Friedrich, Carl J., author
Frederick A. Praeger, 1962
Buku Teks
Lowenthal, Mark M., author
CQ Press, 2009
Buku Teks
Lowenthal, Mark M., author
CQ Press, 2003
Buku Teks
Walker, E. Ronald, author
University of Chicago Press, 1947
Buku Teks
Nickersen, Jane Soames
The Devin-Adair Company, 1961
Buku Teks