Dabars, Zita
McGraw-Hill, 2002
Buku Teks
Ajzen, Icek, author
Open University Press, 2004
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Ajzen, Icek, author
Open University Press, 2005
Buku Teks
Freeborn, Richard, editor
London : MacMillan Press, 1976
Buku Teks
Jenkin, James, author
Lonely Planet Publications, 2006
Buku Referensi