+.SH LDAP versions
+This library supports version 3 of the Lightweight Directory Access
+Protocol (LDAPv3) as defined in RFC 4510. It also supports a variant
+of version 2 of LDAP as defined by U-Mich LDAP and, to some degree,
+RFC 1777. Version 2 (all variants) are considered obsolete.
+Version 3 should be used instead.
+.LP
+For backwards compatibility reasons, the library defaults to version 2.
+Hence, all new applications (and all actively maintained applications)
+should use
+.BR ldap_set_option (3)
+to select version 3. The library manual pages assume version 3
+has been selected.
+.SH INPUT and OUTPUT PARAMETERS
+All character string input/output is expected to be/is UTF-8
+encoded Unicode (version 3.2).
+.LP
+Distinguished names (DN) (and relative distinguished names (RDN) to
+be passed to the LDAP routines should conform to RFC 4514 UTF-8
+string representation.
+.LP
+Search filters to be passed to the search routines are to be
+constructed by hand and should conform to RFC 4515 UTF-8
+string representation.
+.LP
+LDAP URLs to be passed to routines are expected to conform
+to RFC 4516 format. The
+.BR ldap_url (3)
+routines can be used to work with LDAP URLs.
+.LP
+LDAP controls to be passed to routines can be manipulated using the
+.BR ldap_controls (3)
+routines.