* https://docs.oracle.com/javase/jndi/tutorial/ldap/models/x500.html -- overview of x.500 hierarchical directory service
* https://www.isode.com/whitepapers/ic-6033.html -- similarities and differences between #X.500 and #LDAP
* https://en.wikipedia.org/wiki/Active_Directory https://msdn.microsoft.com/en-us/library/aa367008(v=vs.85).aspx https://en.wikipedia.org/wiki/OpenLDAP http://www.openldap.org/ http://directory.fedoraproject.org/ https://wiki.samba.org/index.php/Samba_&_LDAP https://www.microfocus.com/products/open-enterprise-server/ -- Some LDAP implementations

@musicman