Remley, Jim, author
American Management Association, 2005
eBooks
Wendt, Paul Francis, author
McGraw-Hill, 1979
Buku Teks
Siburian, Eveline, author
2017
UI - Tesis (Membership)
Allen, Robert G., author
Pustaka Delaprasta, 1996
Buku Teks
Fraser, W.D.
Macmillan Publishers Ltd., 1984
Buku Teks