static L<WebRelation> web_dropConfirmedPossibles(L<WebRelation> l) {
  if (empty(l)) ret l;
  new HashSet<T3<S>> index;
  for (WebRelation r : l)
    index.add(tripleToLower(web_relationToTriple(r)));
  new Matches m;
  L<WebRelation> out = emptyListWithCapacity(l);
  for (WebRelation r : l)
    if (!(swic(web_text(r), "possibly ", m) && index.contains(
      tripleToLower(t3(web_text(r.a), m.rest(), web_text(r.b))))))
      out.add(r);
  ret out;
}