McCormick, James M., author
Thomson, 2005
Buku Teks
Herrick, Christopher, author
Longman, 2003
Buku Teks
Adams, John S.
Ballinger Publ., 1976
Buku Teks
Wittkopf, Eugene R., author
Thomson wadsworth, 2008
Buku Teks
Eugene R. Wittkopf, James M. McCormick, editor
Rowman & Littlefield publisher INC, 2008
Buku Teks