Altschull, J. Herbert
Longman, 1994
Buku Teks
Bryce, Herrington J, author
Palgrave Macmillan, 2005
Buku Teks
Judd, Dennis R., author
Little, Brown, 1979
Buku Teks
Muller, Herbert J.
Oxford University Press , 1953
Buku Teks
Ballinger Publishing Company, 1981
Buku Teks