Neb. Rev. Stat. §§ 80-203
No money shall be so raised or expended, as provided in section 80-202, until the expiration of twenty days after the passage or adoption of such resolution, motion, or ordinance authorizing the same, and if within that time a petition shall be filed with said supervisors or commissioners of the county, or the commissioners, council or trustees of the city or village, signed by fifteen percent of the legal voters of said county, city or village, asking that such proposition be submitted to a vote of the people, then such proposition shall be submitted to the vote of the people of the county, city or village and shall not become effective until it shall have been approved by a majority of those voting thereon at the next general, special, city or village election held more than thirty days after the filing of said petition.
Neb. Rev. Stat. §§ 80-203