Branson, Richard, author
Virgin Books, 2007
Buku Teks
Tambunan, Emil H., author
Indonesia Publishing House, 2007
Buku Teks
Schuller, Robert H., author
Gunung Mulia, 1986
Buku Teks
Tracy, Brian, author
John Wiley & Sons, 2003
Buku Teks
Bryan Lo`s, author
Awesome Books Publishing SDN BHN, 2002
Buku Teks