Hill, Napoleon, author
Ufuk Press, 2009
Buku Teks
Covey, Stephen R., author
Interaksara, 2000
Buku Teks
Rose, Anthony A., author
McGraw-Hill, 2013
Buku Teks
Kaplan, Burton, author
Prentice-Hall, 1995
Buku Teks
Kaplan, Burton, author
Prentice-Hall, 1996
Buku Teks