20 ILCS 3805/15

The Authority may from time to time, issue renewal notes, issue bonds to pay such notes, and whenever it deems refunding expedient, refund any bonds by the issuance of new bonds, whether the bonds to be refunded have or have not matured, and issue bonds partly to refund bonds then outstanding and partly for any other purpose. The refunding bonds shall be sold and the proceeds applied to the purchase, redemption or payment of the bonds to be refunded.