Neb. Rev. Stat. §§ 17-516
For the purpose of paying the cost of constructing, landscaping, and equipping malls and plazas, paving, repaving, macadamizing or graveling, curbing, guttering, or otherwise improving streets, avenues, or alleys in any improvement district, the mayor and city council of a city of the second class or village board of trustees shall have the power and may, by ordinance, cause to be issued bonds of the city or village to be called District Improvement Bonds of District No. ...., payable in not exceeding fifteen years from date, and to bear interest payable annually or semiannually with interest coupons attached or may issue its warrants, as other warrants are issued, to be called District Improvement Warrants of District No. ...., payable in the order of their number, to be issued in such denominations as may be deemed advisable, and to bear interest. When warrants are issued for the payment of such cost, special taxes and assessments shall be levied sufficient to pay such warrants and the interest thereon within three years from the date of issuance.
Neb. Rev. Stat. §§ 17-516