Artikel Jurnal
White, James J., author
St. Paul Minn, 1988
Buku Teks
edited by Hilary Lewis Ruttley
[publisher not identified], 1995
Buku Teks
Sutherland, Arthur E.
The Foundation Press, Inc., 1953
Buku Teks
Jacobs, Sydney, author
LBC Information Service, 2000
Buku Teks