Doyle, Michael P.
John Wiley & Sons, 1980
Buku Teks
by Robert W. Parry ... [and others]
Prentice-Hall, 1970
Buku Teks
Dannley, Ralph L.
Macmillan, 1968
Buku Teks
Palmer, W.G.
University Press, 1954
Buku Teks
Fishel, Derry L.
Macmillan, 1971
Buku Teks