California Code, Government Code - GOV § 29970

At least once each year within 60 days prior to an interest-payment date, if the sinking fund contains sufficient available money to call one or more of the outstanding bonds, the board shall, by notice published once a week for two successive weeks in some newspaper published in the county, and, in its discretion, in any other newspaper or newspapers, invite sealed proposals for the sale to the county of any bonds for the payment of which the sinking fund was created.  The notice shall state the amount available for redemption of the bonds and specify the time and the place the proposals will be opened.