Bru, Eduard, author
Actar , 2001
Buku Teks
Clarke, Arthur C.
Harper and Row, 1965
Buku Teks
Feiling, Keith
Macmillan, 1951
Buku Teks
Gronbach, Kenneth W., author
American Management Association, 2008
eBooks
Atkinson, William Illsey, author
American Management Association, 2003
eBooks