at</span><span class="special">()</span></code>
        to find an author given a book name and the other way around) and add information
        about the relations that we are sure we will not want to index later (like
        the abstracts). Option 1 is not possible, option 2 neither.
      </p>
<p>
        Boost.Bimap provides support for this kind of situations by means of an embedded
        information member. You can pass an extra parameter to a bimap: <code class="computeroutput"><span class="ident