Lerche, Charles O.
Prentice-Hall, 1958
Buku Teks
Langdon, Robert M., author
Littlefield Adams, 1961
Buku Teks
Bisson, T.A., author
Macmilan Co., 1945
Buku Teks
Wittkopf, Eugene R., author
Thomson, 2002
Buku Teks
Leopold, Richard W., author
Alfred A. Knopf, 1962
Buku Teks