Clark, William R.
John Wiley & Sons, [Date of publication not identified]
Buku Teks
by Robert W. Parry ... [and others]
Prentice-Hall, 1970
Buku Teks SO
Campbell, Donald T.
Rand Mc Nally College Publisher, 1966
Buku Teks
Churchill, Gilbert A.
The Dryden Press, 1995
Buku Teks SO
Churchill, Gilbert A.
Thomson, 2005
Buku Teks