All bonds issued by the corporation shall be payable solely out of the revenue and receipts derived from the leasing or sale by the corporation of its projects or of any thereof as may be designated in the proceedings of the board of directors under which the bonds shall be authorized to be issued. The bonds may be executed and delivered by the corporation at any time, may be in a form and in denominations and of a tenor and maturities, may be in registered or bearer form either as to principal or interest or both, may be payable in installments and at a time or times not exceeding forty years from the date of issuance, may be payable at a place or places whether within or without the State of Nebraska, may bear interest at a rate or rates payable at a time or times and at a place or places and evidenced in a manner, may be executed by officers of the corporation and in a manner, and may contain provisions not inconsistent with this section, as provided in the proceedings of the board of directors authorizing the bonds to be issued. If deemed advisable by the board of directors, there may be included in the proceedings under which bonds of the corporation are authorized to be issued, an option to redeem all or any part of the bonds as specified in the proceedings at a price or prices and after notice or notices and on terms and conditions as set forth in the proceedings and as summarized on the face of the bonds. This section shall not be construed to confer on the corporation any right or option to redeem any bonds except as may be provided in the proceedings under which the bonds are issued. Any bonds of the corporation may be sold at public or private sale in a manner and from time to time as determined by the board of directors to be most advantageous. The corporation may pay all expenses, premiums, and commissions which its board of directors deems necessary or advantageous in connection with the issuance of the bonds. Issuance by the corporation of one or more series of bonds for one or more purposes shall not preclude it from issuing other bonds in connection with the same project or any other project, but the proceedings under which any subsequent bonds are issued shall recognize and protect any prior pledge or mortgage made for a prior issue of bonds, unless in the proceedings authorizing the prior issue the right was reserved to issue subsequent bonds on a parity with the prior issue. Any bonds of the corporation at any time outstanding may at any time be refunded by the corporation by the issuance of refunding bonds in an amount the board of directors deems necessary, but not exceeding an amount sufficient to refund the principal of the bonds to be refunded, together with any unpaid interest on the bonds to be refunded and any premiums and commissions necessary to be paid in connection therewith. Any refunding may be effected whether the bonds to be refunded shall have matured at that time or at a later date, either by sale of the refunding bonds and the application of the proceeds of the refunding bonds for the payment of the bonds to be refunded, or by the exchange of the refunding bonds for the bonds to be refunded with the consent of the holders of the bonds to be refunded, and regardless of whether or not the bonds to be refunded were issued in connection with the same projects or separate projects and regardless of whether or not the bonds proposed to be refunded are payable on the same date or on different dates or are due serially or otherwise. All bonds and the interest coupons applicable to the bonds are negotiable instruments.