Grbich, Carol, author
Allen and Unwin, 1999
Buku Teks
Jacobsen, Kathyn, author
Jones & Bartlett Learning, 2012
Buku Teks
edited by Ann Bowling, Shah Ebrahim
Open University Press, 2007
Buku Teks
Baumgartner, Ted A., author
McGraw Hil , 2013
Buku Teks
Baumgartner, Ted A., author
McGraw-HIll, 2002
Buku Teks