Judd, Dennis R.
Little, Brown, 1979
Buku Teks SO
Bryce, Herrington J
Palgrave Macmillan, 2005
Buku Teks SO
Curran, James
Routledge, 2002
Buku Teks SO
Howard Tumber, editor
Routledge, 2000
Buku Teks SO
Huzzar, George B, De
Thomas Y.Crowell Company, 1955
Buku Teks