Conrad, Peter, author
Thames and Hudson, 1998
Buku Referensi
Jennings, Dean, author
Ulverscroft, 1967
Buku Teks
Hari, Daoud, author
Random House, 2008
Buku Teks
MacNeil, Robert, author
Viking Penguin, 1989
Buku Teks
Hamel, Gary, author
Harvard Business School Press, 2002
Buku Teks