Snyder, Louis L.
D. van Nastrand Company, Inc., 1967
Buku Teks
Brinton, Crane, 1898-1968
Prentice-Hall, 1957
Buku Teks
Hoffding, Harold
Macmillan, 1955
Buku Teks
edited by G. Goodwin
Cambridge University Press, 1958
Buku Teks
Palmer, Robert Roswell, 1909-2002
McGraw-Hill, 1992
Buku Teks