Timperley, John, author
Elex Media Komputindo, 2004
Buku Teks
Office of Research and publications loyola schools,
Majalah, Jurnal, Buletin
Swastha, Basu, author
Liberty , 1997
Buku Teks
Adler, Hans A., author
UI-Press, 1980
Buku Teks
Adler, Hans A., author
Universitas Indonesia (UI-Press), 1983
Buku Teks