Neb. Rev. Stat. §§ 17-153
All taxes levied for the purpose of raising money to pay the interest or to create a sinking fund for the payment of the bonds provided for in section 17-925, shall be payable in money only. Except as otherwise provided, no money so obtained shall be used for any other purpose than the payment of the interest or debt for the payment of which they shall have been raised. Such sinking fund may, under the direction of the mayor and city council, be invested in any of the underdue bonds issued by such city of the second class, and such bonds may be procured by the city treasurer at such rate of premium as shall be prescribed by ordinance. Any due or overdue bond or coupon shall be a sufficient warrant or order for the payment of the same by the city treasurer, out of any fund specially created for that purpose, without any further order or allowance by the mayor and city council.
Neb. Rev. Stat. §§ 17-153