Walter, Paul A.F., author
McGraw-Hill, 1952
Buku Teks
Taylor, Paul C., author
Polity Press, 2013
Buku Teks
Kinloch, Graham C., author
McGraw-Hill , 1974
Buku Teks
Matthews, Basil
Edinburgh House Press, 1927
Buku Teks
Meer, Nasar, author
Sage, 2014
Buku Teks