1. Andrews, B.: Book Burro (2010),
https://addons.mozilla.org/addon/book-burro/
2. AVG: AVG LinkScanner - How it Works (2010),
http://linkscanner.avg.com/ww.sals-how-it-works.html
3. Paprotsky, A.: A Bit Better RTM (2009),
https://addons.mozilla.org/addon/a-bit-better-rtm/
4. Skype: Skype button in Internet Explorer or Firefox toolbar (2005),
http://www.skype.com/intl/en/support/user-guides/toolbar?lang=en