Sewerd, Jack
Lotus Press, 1983
Buku Teks
Blum, Mark
Chronicle Books, 1998
Buku Referensi
Johns, Dean., author
Strategic Information and Research Development Centre , 2009
Buku Teks
[compiled by] Paul F. Boller, Jr. and Ronald Story
Hougton Mifflin, 1988
Buku Teks
Asmita, 2004
Buku Teks