Neb. Rev. Stat. § 60-369

Any purchaser of a motor vehicle or trailer from the State of Nebraska or any political subdivision of the state may operate such motor vehicle or tow such trailer without registration for a period of thirty days. Upon demand of proper authority, satisfactory proof of ownership, which shall be either the certificate of title to such motor vehicle or trailer with assignment thereof duly executed or a bill of sale which describes such motor vehicle or trailer with identification number, shall be presented by the person in charge of such motor vehicle or trailer for examination.