California Code, Public Utilities Code - PUC § 13112

(1) The payment of any such principal, interest or premiums through appropriate reserve funds or special trust accounts, established as hereinafter in this article provided.

(2) The payment of interest on or principal of bonds of any such issue out of sums received as premiums or accrued interest on the sale of that issue.

(3) The payment of any such principal or premiums out of the proceeds of the sale of refunding bonds issued for that purpose.

(4) The payment out of the proceeds of any bonds of the whole or a part of the interest accruing on said bonds during the period of the performance of work to be paid for out of such proceeds.

(5) The payment of any such principal, interest or premiums by the purchasers of any such bonds, or by any entity, public or private, other than the district, in any case where any such purchaser or entity may have guaranteed such payment.