Neb. Rev. Stat. § 23-3587

Within twenty days after the authority has been declared a public corporation and body politic by the county board, the county clerk shall transmit to the Secretary of State a certified copy of the record relating thereto, and the same shall be filed in his office in the same manner as articles of incorporation are required to be filed under the general law concerning corporations. A copy of such record shall also be filed by the county clerk in his own office.