Neb. Rev. Stat. §§ 18-2526
If a majority of the voters voting on an initiative measure pursuant to the Municipal Initiative and Referendum Act shall vote in favor of such measure, it shall become a valid and binding measure of the municipality thirty days after certification of the election results, unless the governing body by resolution orders an earlier effective date or the measure itself provides for a later effective date, which resolution shall not be subject to referendum or limited referendum. A measure passed by such method shall not be amended or repealed except by two-thirds majority of the members of the governing body. No such attempt to amend or repeal shall be made within one year from the passage of the measure by the electors.
Neb. Rev. Stat. §§ 18-2526