The U.S. patent office refuses to assess claims for perpetual motion devices unless the inventors can produce working models.
美国专利局拒绝评估认证永动装置，除非设计者们能制造出可用的模型。
The U.S. patent office refuses to assess claims for perpetual motion devices unless the inventors can produce working models.
美国专利局拒绝评估认证永动装置，除非设计者们能制造出可用的模型。
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