e a polygon
          was located in an interior ring, all touching each other
        </li>
<li class="listitem">
          Fix union which could produce invalid results (for some cases, this needs
          to define BOOST_GEOMETRY_INCLUDE_SELF_TURNS)
        </li>
<li class="listitem">
          Fix intersection (idem), but some cases are still not yet valid
        </li>
<li class="listitem">
          Fix difference (idem), but some cases are still not yet valid
        </li>
<li class="listitem">
    