- “Linux: Prevent From Using Or Reuse Same Old Passwords” by Vivek Gite – http://www.cyberciti.biz/tips/how-to-linux-prevent-the-reuse-of-old-passwords.html
- A very clear article: “Linux Password Security with pam_cracklib” by Hal Pomeranz – http://www.deer-run.com/~hal/sysadmin/pam_cracklib.html
- “System Authentication using LDAP” by Brad Marshall (Plugged In Software) – http://quark.humbug.org.au/publications/ldap/system_auth/sage-au/system_auth.html