e>employee **</code>,</li>
  <li><code>boost::shared_ptr&lt;const employee *></code>.</li>
</ul>
In general, chained pointers with dereferencing distance greater than 1 are not
likely to be used in a normal program, but they can arise in frameworks
which construct "views" as <code>multi_index_container</code>s from preexisting
<code>multi_index_container</code>s.
</p>

<p>
In order to present a short summary of the different usages of Boost.MultiIndex
key extractors in the presence of reference wrappers and