Hall, J. Oliver
Problem solving in our America democracy
America Book Company, 1958
 Buku Teks SO
Hall, John Oliver
Problem solving in our American democracy
American Book Company, 1958
 Buku Teks SO
Smith, R. Nelson
Solving general chemistry problems
W.H. Freeman, 1980
 Buku Teks SO
Democracy and the environment: problems and prospects
edited by William M. Lafferty and James Meadowcroft
Edward Elgar, 1996
 Buku Teks
Carter, Stephen L.
Civility : manners, morals, and the etiquette of democracy / Stephen L. Carter
Basic Books, 1998
 Buku Teks SO