The refunding warrants or bonds shall bear such date, be in such denominations, and mature at such time or times, not exceeding thirty years from date of issue, as the governing body shall determine. Such warrants or bonds may be made subject to redemption at any specified time or times if it is so provided in the initial resolution. Refunding warrants or bonds issued pursuant to this chapter may be designated as “refunding improvement warrants” or “refunding improvement bonds” as the governing body shall determine; provided, that nothing herein shall be deemed to subject such warrants or bonds to chapter 21-03 with reference to general obligation bonds of the municipality. All such warrants or bonds shall be negotiable within the meaning of and for all the purposes specified in title 41 and shall be valid investments for fiduciary, corporate, and public funds to the same extent as improvement warrants or bonds.