Neb. Rev. Stat. § 84-1108: Officers; alternate; oath.

Within thirty days after receiving notice of his appointment, each alternate shall take and subscribe, before any official empowered by law to administer oaths, the same oath or affirmation as is required by law for the officer to whose powers and duties he is designated to succeed, and shall file the same in the office of the filing authority, and his failure so to do within the prescribed period will operate to forfeit his rights under such appointment. No alternate, qualified as above, shall be required to execute any other oath or undertaking or to comply with any other legal formality as a prerequisite to his assumption of the powers and duties to which he is designated to succeed.