Neb. Rev. Stat. §§ 16-809
The provisions of sections 16-801 to 16-811 and of any ordinance authorizing the issuance of bonds under the provisions of sections 16-801 to 16-811 shall constitute a contract with the holders of such bonds, and any holder of a bond or bonds or any of the coupons of any bond or bonds of such city, issued under the provisions of sections 16-801 to 16-811, may either in law or in equity, by suit, action, mandamus, or other proceedings, enforce and compel the performance of all duties required by the provisions of sections 16-801 to 16-811 or by the ordinance authorizing the bonds, including the making and collection of sufficient charges and fees for service and the use thereof, and the application of income and revenue thereof.
Neb. Rev. Stat. §§ 16-809