Axelrod, Rise B.
St. Martin's Press, 1997
Buku Referensi
Axelrod, Rise B.
St. Martin Press, 1997
Buku Referensi
Netzley, Michael
Prentice-Hall, 2001
Buku Teks SO
Beer, David
John Wiley & Sons, 2005
Buku Teks SO
Charles E. Tutle Co.Inc, 1959,
Buku Referensi