"Cyber Security Tip ST04-002". Choosing and Protecting Passwords. US CERT. 21 May 2009. Archived from the original on July 7, 2009. Retrieved June 20, 2009.
"Cyber Security Tip ST04-002". Choosing and Protecting Passwords. US CERT. 21 May 2009. Archived from the original on July 7, 2009. Retrieved June 20, 2009.