Neb. Rev. Stat. § 8-321

No evidence of indebtedness taken by said association for the return of any loan shall be negotiable in form, and whatever be its form, every such evidence of indebtedness shall be nonnegotiable in law, except as hereinafter provided, and no such debt or evidence of debt shall be assignable or transferable in any manner so as to prevent the discharge thereof by payments to the association, except as hereinafter provided, except that bonds and interest-bearing obligations, in which temporary investments may be made as hereinbefore provided, may be converted into cash in due course. Notwithstanding the provision of this section, an association may sell or purchase such loans, and enter into such participation loans, as are or may be permitted to federal savings and loan associations doing business in this state.