Cal. Elec. Code § 9304

Within 10 days after the date of publication or posting, or both, of the notice of intention and statement, the proponents shall file a copy of the notice and statement as published or posted, or both, together with an affidavit made by a representative of the newspaper in which the notice was published or, if the notice was posted, by a voter of the district certifying to the fact of publication or posting. The affidavit, together with a copy of the notice of intention and statement, shall be filed with the district elections official.