Neb. Rev. Stat. § 14-550

When any special assessment is levied within a city of the metropolitan class, it shall be the duty of the city clerk to deliver to the city treasurer a certified copy of the ordinance levying such special assessment, and the city clerk shall append a warrant to such ordinance requiring the city treasurer to collect such special assessment. It shall be the duty of the city clerk to immediately give notice by mail to the owners of the property so assessed, or their agents, if the addresses of such persons can be ascertained, that such assessment will become delinquent on a certain date.