Plucknett, Theodore Frank Thomas
At The University Press, 1958
Buku Teks
Arnstein, Walter L.
Head, 1983
Buku Teks
Barker, Ernest
Oxford University Press, 1942
Buku Teks
Himmelfarb, Gertrude
Weidenfeld and Nicolson,, 1968
Buku Teks
Macmillan, 1984
Buku Teks