Here are the URLs that contain very useful information about LDAP. From these URLs, this HOWTO was made, so if after reading this document you need more specific information, you probably will find here:
University of Michigan LDAP Page: http://www.umich.edu/~dirsvcs/ldap/
University of Michigan LDAP Documentation Page: http://www.umich.edu/~dirsvcs/ldap/doc/
OpenLDAP Administrator's Guide (brother document): http://www.openldap.org/doc/admin
Linux Directory Service: http://www.rage.net/ldap/
Red Hat and LDAP: http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/ref-guide/ch-ldap.html
Mandrake Linux - Using OpenLDAP for Authentication: http://www.mandrakesecure.net/en/docs/ldap-auth.php
Integrating OpenLDAP with other Open Source projects: ftp://kalamazoolinux.org/pub/pdf/ldapv3.pdf
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