pair<bool, string> Esquema::i_buscarAreaTematica2 (Arbre<string> &a, Revista& r) {
    pair<bool, string> p;
    if (a.es_buit()) {
      p.first = false;
      //cout << "Es buit" << endl;
    }
    else if (r.esPC((a.arrel()))) {
      p.first = true;
      p.second = a.arrel();
    }
    else {
      string arrel = a.arrel();
      //cout << "Else: "<<endl;
      Arbre<string> a1, a2;
      a.fills(a1, a2);
      pair<bool, string> p1, p2;
      p1 = i_buscarAreaTematica2 (a1, r);
      p2 = i_buscarAreaTematica2 (a2, r);
      if (p1.first and not p2.first) {
    p.first = true;
    p.second = p1.second;
      }
      else if (not p1.first and p2.first) {
    p.first = true;
    p.second = p2.second;
      }
      else if (p1.first and p2.first) {
    p.first = true;
    p.second = arrel;
      }
      else
    p.first = false;
    }
    return p;
  }