Griffith, Martin
Routledge, 2002
Buku Teks
Jackson, John H.
West Publishing, 2013
Buku Teks
edited by Beth A. Simmons and Richard H. Steinberg
Cambridge University Press, 2006
Buku Teks
Moon, Parker Thomas
Macmillan, 1926
Buku Referensi
Routledge, 1997
Buku Teks