Wiarda, Howard J., author
Thomson Wadsworth, 2000
Buku Teks
Powell, G. Bingham, author
Pearson Education, 2015
Buku Teks
edited by Roy C. Macridis, Bernard E. Brown
Dorsey Press, 1968
Buku Teks
Chilcote, Ronald H., author
Routledge, 2000
eBooks
Curtis, Michael, author
Harper & Row, 1978
Buku Teks