Guillebaud, John
Churchill Livingstone, 1993
Buku Teks
Singh, Jagjit, author
Dover, 1966
Buku Teks
Law, Stephen, author
Quersus, 2013
Buku Teks
Frost, S.E., author
Doubleday, 1962
Buku Teks
Hoevemeyer, Victoria A., author
American Management Association, 2006
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