Maxwell, John C., author
Menuju Insan Cemerlang, 2014
Buku Teks
Covey, Stephen R., author
Simon & Schuster, 2013
Buku Teks
Tracy, Brian, author
American Management Association, 2002
eBooks
Denning, Melita
Llewellyn Publications, 1993
Buku Teks
Reed, Scott
N.Y Parker Pub. Co., 1972
Buku Teks