Benjamin, Jules R., author
St. Martin's Press, 1983
Buku Teks
edited by Mary Abbott
Routledge, 1996
Buku Teks
Selmann, R. R., author
Edward Arnold, 1953
Buku Referensi
edited by Colin Cameron
Sage, 2014
Buku Teks
Hutchinson, Ian H., 1951-, author
Cambridge University Press, 2015
Buku Teks