Collin, P.H.
Peter Collin Publishing, 2001
Buku Teks SO
Greener, Michael
Penguin books, 1994
Buku Referensi
Peter Salim
Modern English Press, 1993
Buku Referensi
Pass, Chirtopher
Erlangga, 1997
Buku Referensi
Kurian, George Thomas
[American Management Association, ], 2013
eBooks