Neb. Rev. Stat. §§ 16-623
For the purpose of paying the cost of improving the streets, avenues, or alleys in an improvement district created pursuant to section 16-619 or 16-624, exclusive of intersections of streets or avenues, or spaces opposite alleys therein, the mayor and city council shall have power and may, by ordinance, cause to be issued bonds of the city, to be called Street Improvement Bonds of District No. ....., payable in not exceeding twenty years from date, and bearing interest, payable either annually or semiannually, with interest coupons attached. In such cases they shall also provide that the special taxes and assessments shall constitute a sinking fund for the payment of the bonds. The entire cost of improving any such street, avenue, or alley, properly chargeable to any lot or land within any such improvement district according to the front footage thereof, may be paid by the owners of such lots or lands within fifty days from the levying of such special taxes, and thereupon such lot or lands shall be exempt from any lien or charge therefor.
Neb. Rev. Stat. §§ 16-623