Allen, Mark, author
Elsevier, 2015
Buku Teks
Jain, Niketa, author
Taylor and Francis, 2017
Artikel Jurnal
edited by Arthur Cotterell
Oxford Oxford University Press , 1980
Buku Teks
Friedland, Bernard
Prentice Hall International, 1996
Buku Teks
Massachusetts Harvard Business School Press, 1988
Buku Teks