交易双方未达成书面合同,在事实难以查明时应根据举证规则,由较易提供证据的一方负举证责任,并同时参考双方的交易习惯来推定事实。 If the parties to the transaction fail to reach a written contract, they should bear the burden of proof by the party who is more likely to provide evidence according to the rules of evidence when the facts are difficult to ascertain, and at the same time make reference to the trading habits of both parties to infer the fact.