Morris, Richard B.
Van Nostrand Reinhold, 1955
Buku Teks SO
Simey, T.S.
Clarendon Press, 1946
Buku Teks
edited by Jack P. Greene, J.R. Pole
Blackwell , 1994
Buku Referensi
Dull, Jonathan R
Yale University Press, 1985
Buku Teks
edited by Edmund S. Morgan
Prentice-Hall, 1965
Buku Teks SO