Helms, Michael E., author
Prentice-Hall, 1990
Buku Referensi
Ziegler, Kathleen, author
Rockport Publishers, 1994
Buku Referensi
Drago, Carl, author
Blackwell, 2014
Buku Teks
Jackson, Paul, author
Chancellor, 1994
Buku Referensi
Microsoft Corporation, 1999
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