Maltz, Maxwell, 1899-1975, author
Interaksara, 2004
Buku Teks
Tracy, Brian, author
American Management Association, 2002
eBooks
Tambunan, Emil H., author
Indonesia Publishing House, 2007
Buku Teks
Covey, Stephen R., author
Simon & Schuster, 1990
Buku Teks
Trump, Donald J.
Mitra Media, 2007
Buku Teks