Hobbs, Christopher J., author
W.B. Saunders , 2001
Buku Referensi
Weiss, Steve Mark, author
American Management Association, 2008
eBooks
Collins, R. Douglas, author
Lippincott, 1997
Buku Referensi
Brown, Lester R., author
W.W.Norton, 1995
Buku Teks
Thibault, Paul J., author
Routledge, 1997
Buku Teks