David L. Andrews, Ben Carrington
Wiley-Blackwell, 2013
Buku Teks
Blanchard, Kendall, author
Bergin & Garvey, 1995
Buku Teks
Peter Craig, author
Learning matters Ltd., 2010
Buku Teks
David R. Mottram, editor
Routledge, 2011
Buku Teks
Cox, Richard H., author
McGraw-Hill, 2012
Buku Teks