Hollick, Ann L.
Princeton University press, 1981
Buku Teks
Sohn, Louis B., author
Thomson Reuters, 2010
Buku Teks
Wesson, Robert G., author
Houghton Miffiln, 1977
Buku Teks
Bohlen, Charles E.
W.W. Norton & Company, 1969
Buku Teks
Hartmann, Frederick H., author
Macmillan, 1985
Buku Teks