Paneth, Donald, author
Facts on File, 1983
Buku Referensi
Herget, James E.
Texas: Rice University Press, 1990,
Buku Referensi
Crotty, William J., author
Little, Brown, 1980
Buku Teks
Horwitz, Morton J., author
Harvard University Press, 1977
Buku Teks
Tribe, Laurence H., author
Foundation Press, 1988
Buku Teks