Wessely, J.E., author
Chicago dsb. Pollett Publ. 1946
Buku Referensi
Wichman, K., author
New York, David Mckay Company
Buku Referensi
Wely, F Prick van, author
London, Cassell
Buku Referensi
Krause, Wayne B
Jakarta: Elex Media Komputerindo, 2002
Buku Teks
Scotland, 1999
Buku Referensi