California Code, Public Resources Code - PRC § 5310

Whenever there is in the sinking fund an amount sufficient for the purpose, the legislative body of the municipality issuing the bonds, may, by ordinance or in such manner as other municipal legislative acts are enacted by it, cause notice to be given by advertisement, stating the amount in the sinking fund available for the redemption of the bonds, and inviting sealed proposals for the redemption, surrender, and cancellation of bonds, with interest, to the specified amount in the sinking fund. At the date designated in the notice the bids, if any, shall be opened and the bids offering to surrender bonds for the lowest sum, not more than par value, shall be accepted.