Knutsen, Torbjorn L.
Manchester University Press, 1992
Buku Teks
Griffith, Martin, author
Routledge, 2002
Buku Teks
Moon, Parker Thomas, author
Macmillan, 1926
Buku Referensi
Routledge, 1997
Buku Teks
Kolodziej, Edward A, author
Cambridge University Press, 2005
Buku Teks