Barker, Eric
Gramedia Pustaka Utama, 2019
Buku Teks
Tracy, Brian
John Wiley & Sons, 2003
Buku Teks SO
Monath, Norman
Pink Books, 2004
Buku Teks SO
Maxwell, John C.
Menuju Insan Cemerlang, 2014
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McGrath, John
Gramedia Pustaka Utama, 2006
Buku Teks SO