 class="keyword">const</span> <span class="identifier">period_type</span> <span class="special">&amp;</span><span class="special">,</span> 
                           <span class="keyword">const</span> <span class="identifier">duration_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">facet_type</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">