California Code, Government Code - GOV § 43791

At least once each year, within sixty 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 legislative body shall invite sealed proposals for the sale to the city of any bonds for payment of which the sinking fund was created.  The invitation shall be by a notice published once a week for two weeks in a newspaper published in the city.  The legislative body may provide for additional publication in other newspapers.