Voice of American Forum Lectures, 1968
Buku Teks
Dicken, Samuel N.
Ginn and comp., 1970
Buku Teks
Getis, Arthur, author
Macmillan, 1985
Buku Teks
Botkin, Daniel B., author
John Wiley & Sons, 2003
Buku Teks
Botkin, Daniel B., author
John Wiley & Sons, 1995
Buku Teks