1. Handley, M.: Why the Internet only just works. BT Technology Journal 24(3) (July 2006)
2. Internet Systems Consortium,
https://www.isc.org/
3. Marshall, B.: How Spam Works (25.09.2003),
http://computer.howstuffworks.com/spam.htm
(July 9, 2009)
4. Graham, P.: A Plan for Spam,
http://www.paulgraham.com/spam.html
5. Levene, M.: An Introduction to Search Engines and Web Navigation. Pearson, London (2005)