the Board of Appeal shall, during proceedings on a case and either of its own motion or following a request from a party to the appeal, refer any question to the Enlarged Board of Appeal if it considers that a decision is required for the above purposes. If the Board of Appeal rejects the request, it shall give the reasons in its final decision; 

In the cases referred to in paragraph 1(a) the parties to the appeal proceedings shall be parties to the proceedings before the Enlarged Board of Appeal.