a name="boost.icl.map.reference"></a><span class="identifier">reference</span><span class="special">;</span>                 
  <span class="keyword">typedef</span> <span class="identifier">base_type</span><span class="special">::</span><span class="identifier">const_reference</span>                                                                                       <a name="boost.icl.map.const_reference"></a><span class="identifier">const_reference</span><span class="special">;</span>           
  <span 