Creighton, Donald G.
Macmillan of Canada, 1970
Buku Teks SO
Toye, William
Oxford University Press , 1959
Buku Teks SO
Southall, Ivan
Melbourne: Oxford University Press, 1964
Buku Teks
Dworkin, Ronald
Harvard University Press, 1986
Buku Teks
Dworkin, Ronald
Fontana Press, 1991
Buku Teks SO