McCoubrey, Hilaire
Brookfield Dartmouth , 1995
Buku Teks
Woodham, Jonatham M.
Oxford University Press, 1997
Buku Teks SO
Chant, Christopher
London: Chancellor Press, 1999,
Buku Referensi
edited by Jack A. Goldstone, Ted Robert Gurr, Farrokh Moshiri
Westview Press, 1991
Buku Teks SO
Black, C.E.
Alfred A. Knopf, 1961
Buku Teks SO