consultant editor, Michael Armstrong
AP Information Services, 1997
Buku Referensi
Maurois, A. (Andre)
Paris Grasset 1930
Buku Teks
Read, Herbert
Longmans , 1961
Buku Teks
Heck, Harold J.
American Management Association, 1972
Buku Teks
Schonberger, Richard John
Business Publications , 1981
Buku Teks