Any bonds issued and sold pursuant to this chapter may be refunded by the issuance of refunding bonds in accordance with Article 6 (commencing with Section 16780) of Chapter 4 of Part 3 of Division 2 of Title 2 of the Government Code. Approval by the electors of the state for the issuance of bonds shall include the approval of the issuance of any bonds issued to refund any bonds originally issued or any previously issued refunding bonds.