Peter Salim
Modern English Press, 1993
Buku Referensi
Pass, Chirtopher
Erlangga, 1997
Buku Referensi
Collin, P. H.
Peter Collin Publishing, 2001
Buku Teks
Kurian, George Thomas
[American Management Association, ], 2013
eBooks
Oxford reference
Oxford University Press, 1990
Buku Referensi