Loader, Ian, author
Routledge, 2011
Buku Teks
Ferrell, Jeff, author
Sage, 2008
Buku Teks
Barnes, Harry Elmer, author
Prentice Hall of India, 1966
Buku Teks
Barkan, Steven E., author
Prentice-Hall, 2012
Buku Teks
Barkan, Steven E., author
Pearson/Prentice Hall, 2006
Buku Teks