Etter, Delores Maria, 1947-
Prentice-Hall, 2002
Buku Teks SO
Palm III, Wiliam J.
Mc Graw Hill, 2011
Buku Teks SO
Gilat, Amos
John Wiley & Sons, 2011
Buku Teks
Devijver, Pierre A.
Prentice-Hall International, 1982
Buku Teks SO
Brandimarte, Paolo
Wiley-Interscience, 2006
Buku Teks SO