Orum, Anthony M., author
Blackwell, 2003
Buku Teks
Cambridge University Press, 2010
eBooks
Jones, John Walter, 1892-1973
At The Clarendon Press, 1956
Buku Teks
Hayes, Carlton J. H.
Macmillan, 1955
Buku Teks
Kviz, Frederick J.
Litle, Brown & Co, 1980
Buku Teks