Snyder, Houis L.
Princeton University Press, 1964
Buku Teks
Mende, Tibor
The Noonday Press, 1953
Buku Teks
Kegley, Charles W. (Charles William), Jr., author
Wardsworth, 2010
Buku Teks
Deborin, G., author
Progress Publishers, 1979
Buku Teks
Schuman, Frederick L., author
McGraw-Hill, 1969
Buku Teks