Neb. Rev. Stat. § 57-201

When any oil, gas, or other mineral lease heretofore or hereafter given on land situated in any county of Nebraska, and recorded therein, shall become forfeited, it shall be the duty of the lessee, his successors or assigns, within thirty days after the date of the forfeiture, to have such lease surrendered in writing, such surrender to be signed and acknowledged by the party making the same and placed on record in the county where the leased land is situated without cost to the owner thereof.