Nebraska Revised Statute 13-2544
Chapter 13 Section 2544
Issuance of bonds; right to contest; procedure.
For a period of thirty days after such publication, any interested person shall have the right to contest the legality of such resolution or proceeding or any bonds which may be authorized thereby, any provisions made for the security and payment of such bonds, or any contract of purchase, sale, or lease relating to the issuance of such bonds. After such time no one shall have any cause of action to contest the regularity, formality, or legality thereof for any cause whatsoever.