Murray, Michael
Atria Books, 2005
Buku Referensi
Werbach, Melvyn R.
Thorsons, 1993
Buku Referensi
Heinerman, John
Prentice-Hall, Paramus, N.J., 1998
Buku Teks SO
Murray, Michael T.
Three Rivers Press, 1996
Buku Teks SO
Stevenson, Gladys T.
John Wiley & Sons, 1960
Buku Teks SO