Cammack, Paul Anthony
Macmillan, 1993
Buku Teks
edited by Roy C. Macridis
Prentice-Hall, 1992
Buku Teks
Kegley, Charles William, Jr.
Wadsworth, 2009
Buku Teks
Rourke, John T.
Mc Graw Hill, 2009
Buku Teks
Barnes, James F.
St. Martin`s Press, 1980
Buku Teks