Cal. Elec. Code § 9304

Within 10 days after the date of publication or posting, or both, of the notice of intention and statement of the reasons for the proposed petition, the proponents shall file with the district elections official a copy of the notice and statement as published or posted, or both, together with the written text of the initiative and 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.