1. The law governing a contractual obligation under this Regulation shall apply to the extent that, in matters of contractual obligations, it contains rules which raise presumptions of law or determine the burden of proof.

2. A contract or an act intended to have legal effect may be proved by any mode of proof recognised by the law of the forum or by any of the laws referred to in Article 11 under which that contract or act is formally valid, provided that such mode of proof can be administered by the forum.