Griffiths, Percival, Sir, 1899-, author
Frederick A. Praeger, 1962
Buku Teks
Sayers, R.S., author
Oxford University Press , 1967
Buku Teks
edited by Charles R. Craig, Robert E. Stitzel
Little, Brown, 1982
Buku Teks
Wheare, K. C., author
Oxford University Press, 1975
Buku Teks
Etzioni, Amitai, author
Prentice-Hall, 1964
Buku Teks