Neb. Rev. Stat. §§ 19-402
If a petition to adopt the commission plan of government is filed with the city clerk of any city meeting the requirements of section 19-401, signed by registered voters equal in number to at least twenty-five percent of the votes cast for all candidates for mayor at the last preceding general city election, the mayor of the city shall, within twenty days after such filing, call and proclaim a special election to be held upon a date fixed in such proclamation, which date shall not be less than fifteen nor more than sixty days after the date and issuance of such proclamation. After the filing of any petition provided for in this section, no signer of such petition shall be permitted to withdraw his or her name from such petition. At such special election the proposition of adopting the commission plan of government shall be submitted to the registered voters of the city, and such proposition shall be stated as follows: Shall the city of (name of city) adopt the commission plan of city government? The special election shall be held and conducted, the vote canvassed, and the result declared in the same manner as provided for the holding and conducting of the general city election in any such city. All officers charged with any duty respecting the calling, holding, and conducting of such general city election shall perform such duties for and at such special election.
Neb. Rev. Stat. §§ 19-402