McGrath, John, author
Gramedia Pustaka Utama, 2006
Buku Teks
Denning, Melita
Llewellyn Publications, 1993
Buku Teks
Robbins, Anthony
A Freeside Book, 1991
Buku Teks
Tracy, Brian, author
American Management Association, 2002
eBooks
Waitley, Denis, author
Glencoe ; MCGraw-Hill, 1997
Buku Teks