Ver Steeg, Clarence L., author
Harper and Row, 1981
Buku Teks
by Mary Beth Norton. .. [et.al.]
Houghton-Miffiln, 1988
Buku Teks
Brinkley, Alan, author
McGraw-Hill, 1997
Buku Referensi
Ver Steeg, Clarence L., author
Harper & Row , 1971
Buku Teks
Noble, David W
University of minnesota press, 2002
Buku Teks