Bwalya, Kelvin Joseph, editor
Chandos, 2014
eBooks
Garland, Eric, author
American Management Association, 2007
eBooks
Hiltrop, Jean Marie
Prentice-Hall, 1995
Buku Teks
Kennedy, Gavin, author
Harvard Business School Press, 994
Buku Referensi
Camp, Jim
Kelompak Gramedia, 2002
Buku Teks