Bonds may be refunded, but no bonds may be refunded under this chapter unless the bonds either mature or are callable for prior redemption under their terms within thirty years from the date of issuance of the refunding bonds, or unless the holder or holders of the bonds voluntarily surrender them for exchange or payment. Outstanding bonds of more than one issue     or series and bonds for refunding and other bonds to construct, furnish, or equip any building or addition or other campus improvement for which bonds are authorized may be combined into one issue or series and may provide for and restrict the combination of future series with the issue. Except as otherwise provided in this section, the bonds must have such details and must be authorized and issued in the manner provided in this chapter. Refunding bonds so issued may carry forward for the payment of the refunding bonds such security and sources of payment as were pledged to the payment of the bonds refunded, and a combined issue of refunding and other bonds may combine such security and sources of payment with a pledge of the revenues of buildings or other campus improvements acquired in whole or in part from the proceeds of the issue, including the security and sources of payment of any future series of refunding bonds or revenues of any building or other campus improvement acquired from the proceeds of a future series if and to the extent that provision is made for combination of future series with the issue. The word “building” as used in this section means all the buildings or other campus improvements the revenues of which are pledged. Any bonds issued for refunding purposes may be delivered in exchange for the outstanding bonds authorized to be refunded, sold at either public or private sale, or sold in part and exchanged in part. There is no interest rate ceiling on those issues issued solely for refunding purposes. The sale price may exceed the principal amount of refunding bonds and the excess may be used to provide for payment of redemption premiums of the bonds to be refunded and to provide for expenses of the issuance and sale of the bonds and the retirement of the outstanding bonds. All other proceeds of the sale must be, to the extent needed, immediately applied to the retirement of the bonds to be refunded, or the proceeds or investments thereof must be placed in escrow to be held and applied to the payment of the bonds to be refunded, or in the case of crossover refunding, must be invested in securities irrevocably appropriated to the payment of principal and interest on the refunding bonds until the date the proceeds are applied to the payment or redemption of the bonds to be refunded.

The proceeds may, in the discretion or pursuant to covenant of the board, be invested in obligations of the United States of America, or in obligations fully guaranteed by the United States of America, but the obligations so purchased must have such maturities and bear such rates of interest payable at such times as will assure the existence of money sufficient to pay the bonds to be refunded when due or when redeemed pursuant to call for redemption, together with any interest and redemption premiums. The proceeds or obligations so purchased must be deposited in trust with the trustee for the refunded bonds, or with the banking corporation, association, or limited liability company which is the paying agent for the refunded bonds, or with the state treasurer, to be held, liquidated, and the proceeds of such liquidation paid out for the payment of the bonds to be refunded and interest and redemption premiums thereon as the refunded bonds become due or subject to redemption under call for redemption previously made, or upon earlier voluntary surrender thereof with the consent of the board. The determination of the board in issuing refunding bonds that the issuance and sale of refunding bonds is necessary for the best interests of the institution and that the limitations herein imposed upon the issuance of refunding bonds have been met is conclusive in the absence of fraud or arbitrary and gross abuse of discretion.