That where bonds heretofore issued by New Mexico normal university [New Mexico highlands university] are held by the state treasurer and which were purchased with the permanent funds of such institution and held for its account, and which by their terms are not now subject to call for the retirement or refunding, the board of regents of New Mexico normal university [New Mexico highlands university], with the approval of the state finance board, may refund such bonds under the provisions of this act [21-3-13, 21-3-14, 21-3-16 to 21-3-28 N.M. Stat. Ann.] by the issuance of refunding bonds for such time and at a rate of interest not exceeding the interest provided in the original issue as may be determined by such board of regents.