Magruder, Frank Abbott
Allyn and Bacon, 1939
Buku Teks
Griffith, Martin, author
Routledge, 2002
Buku Teks
edited by Beth A. Simmons and Richard H. Steinberg
Cambridge University Press, 2006
Buku Teks
Moon, Parker Thomas, author
Macmillan, 1926
Buku Referensi
Routledge, 1997
Buku Teks