Covey, Stephen R., author
Binarupa Akasara, 2002
Buku Teks
Agness, Lindsey, author
Ufuk Press, 2012
Buku Teks
Gratzon, Fred, author
Penerbit Gemilang , 2019
Buku Teks
Scott, Steven K.
Think, 2006
Buku Teks
Ferriss, Timothy, author
Vermilion, 2011
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